Many visitors to the site ask us, “I’ve got a .223 and .308. What will a 6mmBR Norma (6BR) give me that I’m not getting already?” Well first you will probably average consistently smaller groups than your current .223 or .308 rifle (assuming the 6BR has a quality barrel and trigger). A good .308 Winchester can be superbly accurate, no question about that, but the lesser recoil of the 6BR works in the shooter’s favor over a long string of fire. Even with a Rem 700 or Savage action factory action, a 6BR with a benchrest stock, premium barrel, and a high-quality chambering job should deliver 5-shot groups in the high twos to mid-threes, provided you do your job. We have one 6BR rifle that shoots Lapua factory-loaded 6BR ammunition in the low twos and high ones. That’s exceptional, we admit, but it still shows how the 6BR is an inherently accurate cartridge, even with factory loads.
Compared to a .223, the 6BR offers a much better selection of high-BC projectiles, and will deliver considerably more power on the target. So it’s a better choice for hunters and 600-yard benchrest shooters. Compared to the .308 Win shooting 168gr MatchKings, a 6BR shooting 105-107gr bullets offers better ballistics all the way out to 1000 yards. Plus, for most people, the 6BR is just easier to shoot than a .308 Win. Recoil is less than half of the .308 Win cartridge. Both the .308 and 6BR chamberings offer good barrel life, but the 6BR uses 15-18 grains less powder, saving you money. On the other hand the .308 Win is the designated cartridge for F-TR and Palma shooting, so it may be a more versatile chambering for Long-Range competition. So which would we choose between the 6BR and the .308? Actually we think you should have both. The 6BR is a favorite cartridge out to 500 yards, and we like the .308 Win for F-TR. The .308 Win has shown outstanding accuracy, as displayed last week at the NRA F-class Nationals in Arizona.
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Instead of using the standard .223 Remington or 5.56x45mm NATO round, you have many options for an AR-15. Dozens of cartridge variants have been tried in AR-15s. Some of the most noteworthy and popular alternative chamberings for AR-15s are:
20 Practical — This is simply the .223 Rem necked down to .204 caliber. Requires new barrel. Same bolt, same magazines. Best bang for the buck. .224 Valkyrie — A necked-down version of the 6.8 SPC, the .224 Valkyrie was introduced by Federal a few seasons back. It has better ballistics than the .223 Remington, if used with a suitable barrel. 6mm ARC — Relatively new cartridge that works well for varminting, self-defense, tactical competitions, and deer hunting. Good selection of bullets and factory-loaded ammunition. 6.5 Grendel — Accurate and proven across the course, the 6.5 Grendel requires a new barrel, bolt, and magazines. Most use the 6.5 Grendel for competitive shooting and/or hunting. .300 Blackout — Moderately expensive, the .300 Blackout requires a barrel change. This is used for home defense, and hunting. WARNING — with some bullets this round can be chambered in a .223 Rem barrel, with disastrous consequences. .458 SOCOM — Pretty expensive, requires new barrel and bolt. The .458 SOCOM round is typically used for hunting though it was originally designed for Close Quarters Battle (CQB).
Of these six options, our favorite is the 20 Practical, followed by the 6mm ARC and 6.5 Grendel. The 20 Practical is a great varminting round. Check out our featured 20 Practical AR Rifle Report. This 20 Practical cartridge is highly effective on small varmints, and has shown outstanding accuracy in AR-platform rifles crafted by Robert Whitley.
20 Practical — High-Velocity, Affordable Alternative
The 20 Practical is simply a .223 Remington necked down to .204 caliber. This efficient little cartridge can launch 32-grainers at over 4200 fps, with impressive results on P-Dogs. This makes the 20 Practical a great choice for an AR-based varmint rifle.
20 Practical Ultimate Varminter
A decade ago, as a “proof-of-concept”, AccurateShooter.com created a 20 Practical AR15 Ultimate Varminter with a custom 20-caliber upper from Robert Whitley of AR-X Enterprises, LLC. That project rifle was ultra-accurate — every 5-shot group out of the gun was less than the size of a dime. That gun was auctioned off, but Robert Whitley continues to produce custom 20 Practical AR15 uppers. (The 20 Practical cartridge is simply the .223 Rem necked down to 20 caliber — you can use standard .223 brass and load with standard .223 Rem dies. Just swap in a smaller expander and use smaller neck bushings.)
6mm ARC — Popular New SAAMI Cartridge Promoted by Hornady
In June 2020, Hornady introduced the 6mm ARC, a new SAAMI cartridge optimized for AR-platform rifles*. The new 6mm ARC is basically a 6.5 Grendel necked down to 6mm, with the shoulder moved back around .030″. That pushed-back shoulder does reduce case capacity (and velocity), but we assume Hornady did that to create a shorter, proprietary chamber so people could not simply neck-down Lapua 6.5 Grendel brass, as has been done for years with Robert Whitley’s outstanding 6mm AR wildcat.
What Is the 6mm ARC Cartridge? The 6mm ARC cartridge is a modern SAAMI-spec cartridge based on the 6.5 Grendel case necked down for 6mm bullets, with the shoulder moved back 0.030. Yes it is designed to run in AR15-platform rifles. You’ll need a new barrel, bolt, and mags. If you already have an AR chambered in 6.5 Grendel, the ONLY thing you need to change is the barrel. Everything else — bolt, magazines, gas system – is compatible with 6mm ARC.
▶ Official SAAMI Cartridge (not wildcat)
▶ Fits standard AR15-platform rifles
▶ Fits Short/Mini action bolt rifles
▶ Efficient short, fat case design
▶ 30-degree case shoulder
What Do I Need To Shoot the 6mm ARC?
Faxon and Ballistic Advantage are already producing barrels, with more manufacturers sure to follow. All the other required components are already on the market for 6.5 Grendel rifles. Aero Precision already offers complete 6mm ARC uppers.
If you’re converting a standard 5.56×45 mm (.223 Rem) AR15 upper to shoot 6mm ARC, you’ll need a 6mm barrel, a Type II 6.5 Grendel bolt carrier group, and new magazines. Some folks have suggested standard AR mags will work, but trust us, you want the magazines that have been designed for 6.5 Grendel. All the hardware you need is currently available at Brownells.
While 6-6.5 Grendel shooters are known to run stout pressures, the new 6mm ARC cartridge has a relatively moderate Maximum Average Pressure (MAP) rating of 52,000 psi according to the official SAAMI specifications. For a variety of reasons, is wise to keep pressures in a semi-auto rifle moderate. Don’t chase the velocities you might get in a bolt-action gun.
The 6.5 Grendel — Accurate, Plus Good for Hunters
The 6.5 Grendel round is one of the most accurate cartridges for the AR-15 platform. The 6.5 Grendel round offers a larger-diameter, .264-caliber (6.5mm) bullet running at good velocities. This provides ample energy for smaller game and deer. The 6.5 Grendel is often used for hunting deer up to 300 yards.
History of the 6.5 Grendel Cartridge
The 6.5 Grendel originated as a 6mm PPC necked up to 6.5 mm. After Alexander Arms relinquished the “6.5 Grendel” Trademark, the 6.5 Grendel was standardized as an official SAAMI cartridge. It has become popular with target shooters and hunters alike because it is accurate, efficient, and offers modest recoil. Good for small to medium game, the 6.5 Grendel has been offered in lightweight hunting rifles, such as the Howa 1500 Mini Action.
.224 Valkyrie Cartridge — Impressive with Heavy .22-Cal Bullets
The new .224 Valkyrie was introduced in 2019 as a Hot Rod cartridge that will work in AR15s. Basically a 6.8 SPC necked down to .22 caliber, the Valkyrie has a shorter case than the .223 Remington (and 5.56×45 NATO). This allows you to load the longest, heaviest .224-caliber bullets and still feed reliably from an AR15-type magazine. Designed to rival the .22 Nosler while still running well in ARs, the .224 Valkyrie offers excellent long-range performance when loaded with modern, high-BC bullets. We expect some bolt-action PRS shooters might adopt the .224 Valkyrie. Why? Reduced recoil. With the 90gr SMK, the .224 Valkyrie offers ballistics similar to the 6.5 Creedmoor but with significantly less felt recoil. It can also be a viable alternative to a .22-250 for varminters using an AR platform.
Our friend Gavin Gear of UltimateReloader.com found a superbly accurate load with Berger 80.5gr bullets. Watch this video to learn more:
Sierra Bullets has published extensive load data for the .224 Valkyrie. This covers over a dozen powder types — many more than the Hodgdon database. Sierra’s .224 Valkyrie load data covers projectiles from 50 grain all the way up to 95 grains. With the 90 to 95 grain bullets, the little Valkyrie can give 6mm match cartridges a real run for their money — offering similar ballistics with less recoil. When selecting a barrel for the long .224-cal bullets, specify a fast enough twist rate: “Sierra recommends a 1:6.5″-twist barrel for the #9290 22 cal 90 gr HPBT bullet. However, for cartridges like the Valkyrie, that can push them over 2650 fps muzzle velocity, a 1:7″-twist barrel will stabilize the bullet correctly.”
CLICK HEREto DOWNLOAD Complete Sierra .224 Valkyrie LOAD DATA.
.224 Valkyrie vs. .22-250 Remington
The Social Regressive explains: “There are two key reasons why the .224 Valkyrie is unique and desirable. First, it is specifically designed to fit the limitations of the AR-15 platform. It does so even when loaded with gigantic bullets, like the 90-grain SMK that Federal announced. The .22-250 Rem is too long and too fat to work in the AR-15 platform; it needs an AR-10 bolt and magazine.”
The .224 Valkyrie has been marketed as a low-recoil round that can stay supersonic to 1300 yards and beyond (with 90gr Sierra MatchKings). Here a Sniper’s Hide duo shots an AR-platform .224 Valkyrie at distances out to 1550+ yards. To be honest, the accuracy wasn’t that impressive. However this test confirms that the .224 Valkyrie does launch the long, heavy projectiles at high enough velocities to prove superior to the standard .223 Rem. Frank Galli (aka “Lowlight”) teams up with Brian Whalen of Colorado Precision Rifle at the Blue Steel Ranch in New Mexico.
The .300 Blackout — Risky Business
The .300 Blackout appeals to folks who want a .30-caliber defense round. This can be loaded at various velocities. Loaded at subsonic speeds and shot with a suppressor, the .300 BLK offers very low sound levels. Unfortunately, that .300 Blackout cartridge can fit in a .223 Rem chamber. Shooting a .308-caliber bullet in .223 bore is a recipe for disaster.
The .300 AAC Blackout aka “300 BLK”, is a compact 30-caliber cartridge designed to work in AR-15 rifles. It has a shorter cartridge case to accommodate the bigger 30-caliber bullet while still fitting in a standard AR-15 magazine. Unfortunately, that’s the danger. A careless shooter can toss a .300 Blackout cartridge in with .223 Rem rounds without noting. And because the case-head size is the same as the .223 Rem (5.56×45) the rifle’s bolt assembly will happily chamber and fire the .300 BLK round. Problem is, that forces a .308 diameter bullet down an undersized .223-caliber bore. Not good!
This images were provided by Tactical Rifle Shooters on Facebook. The message was clear: “Don’t try to run 300 Blackout in your .223/5.56mm. It won’t end well. The problem is identical rifles and identical magazines but different calibers.”
Image from Accurate Shooter Forum. Cutaway shows the jammed .30-Cal bullet:
For those who MUST have a .300 Blackout, here are some things you can do:
1. Use different colored magazines for .300 Blackout vs. .223 Remington.
2. Mark .223 Rem upper handguards with the caliber in bright paint.
2. Fit all your uppers with caliber-labeled ejection port covers.
4. Mark all .300 BLK Rounds with heavy black marker.
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The U.S. Army Marksmanship Unit regularly published a reloading “how-to” article on the USAMU Facebook page. One excellent “Handloading Hump Day” post covered preparation of once-fired 5.56x45mm brass. This article, the first in a 3-part series, has many useful tips. If you shoot a rifle chambered in .223 Rem or 5.56x45mm, this article is worth reading. You can obtain once-fired Lake City 5.56x45mm brass for less than half the cost of premium .223 Rem brass.
This week, Handloading Hump-Day will answer a special request from several competitive shooters who asked about procedures for morphing once-fired GI 5.56mm brass into accurate match brass for NRA High Power Rifle use. The USAMU has used virgin Lake City (LC) 5.56 brass to win National Championships and set National Records for many years. In this 3-part series, we’ll share techniques proven to wring match-winning accuracy from combat-grade brass.
GI brass has an excellent attribute, worth noting — it is virtually indestructible. Due to its NATO-spec hardness, the primer pockets last much longer than most commercial brass when using loads at appropriate pressures.
Preparing Once-Fired GI 5.56 Brass for Reloading (Part 1 of 3)
Assuming our readers will be getting brass once-fired as received from surplus dealers, the following steps can help process the low-cost raw material into reliably accurate components.
1. Clean the Brass
First, clean the brass of any dirt/mud/debris, if applicable. Depending on the brass’s condition, washing it in a soap solution followed by a thorough rinsing may help. [This step also extends the life of the tumbling media.] Approaches range from low-tech, using gallon jugs 1/2 full of water/dish soap plus brass and shaking vigorously, to more high-tech, expensive and time-consuming methods.
2. Wet-Tumbling Options (Be Sure to Dry the Brass)
When applying the final cleaning/polish, some use tumblers with liquid cleaning media and stainless steel pins for a brilliant shine inside and out, while others take the traditional vibratory tumbler/ground media approach. Degree of case shine is purely personal preference, but the key issue is simple cleanliness to avoid scratching ones’ dies.
If a liquid cleaner is used, be SURE to dry the cases thoroughly to preclude corrosion inside. One method is to dump the wet brass into an old pillow case, then tilt it left/right so the cases re-orient themselves while shifting from corner to corner. Several repetitions, pausing at each corner until water stops draining, will remove most water. They can then be left to air-dry on a towel, or can be dried in a warm (150° F-200° F max) oven for a few minutes to speed evaporation.
Shown below are Lake City cases after cleaning with Stainless Media (STM). Note: STM Case cleaning was done by a third party, not the USAMU, which does not endorse any particular cleaning method.
NOTE: The USAMU Handloading (HL) Shop does not RE-load fired 5.56 brass. We use virgin LC brass with our chosen primer already staked in place. However, our staff has extensive personal experience reloading GI brass for competition, which will supplement the Shop’s customary steps. In handloading, as in life, there are many ways to accomplish any given task. Our suggestions are note presented as the “only way,” by any means. Time for loading/practicing is always at a premium. Readers who have more efficient, alternative methods that maintain top accuracy are invited to share them here.
3. Inspect Every Case
Once dry, inspect each case for significant deformation (i.e., someone stepped on it), damaged mouths/necks and case head/rim damage. Some rifles’ ejectors actually dig small chunks of brass out of the case head — obviously, not ideal for precision shooting. Similarly, some extractors can bend the case rims so badly that distortion is visible when spinning them in one’s fingers. These can be used for plinking, but our match brass should have straight, undamaged rims.
Dented case mouths are common, and these can easily be rounded using a conical, tapered tool, [such as a .223 expander mandrel. A dummy 7.62 or .30-06 cartridge with a FMJ spitzer can also work.] If most of your brass is of one headstamp, this is a good time to cull out any odd cases.
4. Check the Primers Before Decapping
Your clean, dry and inspected brass is now ready for full-length sizing, decapping and re-priming. Historically, primer crimps on GI brass have caused some head-scratching (and vile language) among handloaders. Our next installment will detail efficient, easy and practical methods to remove primer crimp, plus other useful handloading tips. Until next week, Good Shooting!
Accuracy Potential of Mil-Surp 5.56×45 Brass
So, how accurate can previously-fired GI surplus brass be in a good National Match AR-15? Well, here’s a data point from many years ago that might be of interest. A High Power shooter who wrote for the late Precision Shooting magazine took a Bill Wylde-built AR match rifle to a registered Benchrest match. He had no difficulty obtaining consistent 0.5-0.6 MOA accuracy at 200 yards using LC brass and a generic “practice” load that was not tuned to his rifle.
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Do you shoot an AR-15? Then here is a great deal on mil-spec 5.56x45mm ammo made by Federal. Credit Ammoland.com for finding this bargain-priced bulk pack with 400 XM193 rounds for just $274.99, 31% off the regular $399.95 price. That works out to under 69 cents per round. You could pay that much just for the quality Lake City brass!
Firearms products dealer Bereli is offering NEW, factory-fresh Federal XM193 5.56 Ammo loaded with 55gr FMJ Bullets. With this deal you get 400 rounds, plus an Ammo Can for $274.99. That is just $0.687 per round. Plus, with this 400rd Ammo Can ships for free with Code “FREESHIPPING”.
Federal XM193 5.56 Ammo 55 Grain FMJ
Federal 5.56 ammunition is loaded with Lake City brass and works for target shooting, training, and plinking. This ammunition is new production, non-corrosive, in boxer-primed, brass cases, 55 grain, with FMJ-BT. Get 400 rounds for less than $0.69 per round.
Manufacturer: Federal Premium
Caliber: 5.56×45mm
Bullet Weight: 55 gr
Bullet Type: FMJ
Quantity: 400 Rounds
With ammunition in short supply these days, we know ammo production is on people’s minds. Top industry leaders have said the USA will face ammo shortages well into 2021. So ammo-makers big and small are ramping up production to meet demand. If you’re curious how ammunition is created on the assembly by a relatively small, speciality manufacturer, watch the video below to see the entire process, start to finish.
This video from Fog Ammunition reveals how .223 Rem ammo is made. Starting with boxes of bullets and bags of cartridge brass, this video shows how components are bulk-sorted, then .223 Rem ammunition is produced on a modern, linear multi-stage loading machine. In assembly-line fashion, cases are primed, powder is added, bullets are placed, final seating depth is set, and then the case is crimped.
If you’ve never seen an automated loader in action you should definitely watch this video. With this kind of machine, a new round is produced every second or so (see video 1:15 to 1:55). The .223 Remington ammunition featured in this video is loaded with Sierra BlitzKing bullets. Fog offers both rifle and pistol ammo loaded with quality components.
Video Shows Automated Loading Process Start to Finish (Worth Watching):
Remember when primers were plentiful and priced affordably?
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The U.S. Army Marksmanship Unit regularly publishes a reloading “how-to” article on the USAMU Facebook page. One excellent “Handloading Hump Day” post covered preparation of once-fired 5.56x45mm brass. This article, the first in a 3-part series, has many useful tips. If you shoot a rifle chambered in .223 Rem or 5.56x45mm, this article is worth reading.
This week, Handloading Hump-Day will answer a special request from several competitive shooters who asked about procedures for morphing once-fired GI 5.56mm brass into accurate match brass for NRA High Power Rifle use. The USAMU has used virgin Lake City (LC) 5.56 brass to win National Championships and set National Records for many years. In this 3-part series, we’ll share techniques proven to wring match-winning accuracy from combat-grade brass.
GI brass has an excellent attribute, worth noting — it is virtually indestructible. Due to its NATO-spec hardness, the primer pockets last much longer than most commercial brass when using loads at appropriate pressures.
Preparing Once-Fired GI 5.56 Brass for Reloading (Part 1 of 3)
Assuming our readers will be getting brass once-fired as received from surplus dealers, the following steps can help process the low-cost raw material into reliably accurate components.
1. Clean the Brass
First, clean the brass of any dirt/mud/debris, if applicable. Depending on the brass’s condition, washing it in a soap solution followed by a thorough rinsing may help. [This step also extends the life of the tumbling media.] Approaches range from low-tech, using gallon jugs 1/2 full of water/dish soap plus brass and shaking vigorously, to more high-tech, expensive and time-consuming methods.
2. Wet-Tumbling Options (Be Sure to Dry the Brass)
When applying the final cleaning/polish, some use tumblers with liquid cleaning media and stainless steel pins for a brilliant shine inside and out, while others take the traditional vibratory tumbler/ground media approach. Degree of case shine is purely personal preference, but the key issue is simple cleanliness to avoid scratching ones’ dies.
If a liquid cleaner is used, be SURE to dry the cases thoroughly to preclude corrosion inside. One method is to dump the wet brass into an old pillow case, then tilt it left/right so the cases re-orient themselves while shifting from corner to corner. Several repetitions, pausing at each corner until water stops draining, will remove most water. They can then be left to air-dry on a towel, or can be dried in a warm (150° F-200° F max) oven for a few minutes to speed evaporation.
Shown below are Lake City cases after cleaning with Stainless Media (STM). Note: STM Case cleaning was done by a third party, not the USAMU, which does not endorse any particular cleaning method.
3. Inspect Every Case
Once dry, inspect each case for significant deformation (i.e., someone stepped on it), damaged mouths/necks and case head/rim damage. Some rifles’ ejectors actually dig small chunks of brass out of the case head — obviously, not ideal for precision shooting. Similarly, some extractors can bend the case rims so badly that distortion is visible when spinning them in one’s fingers. These can be used for plinking, but our match brass should have straight, undamaged rims.
Dented case mouths are common, and these can easily be rounded using a conical, tapered tool, [such as a .223 expander mandrel. A dummy 7.62 or .30-06 cartridge with a FMJ spitzer can also work.] If most of your brass is of one headstamp, this is a good time to cull out any odd cases.
4. Check the Primers Before Decapping
Your clean, dry and inspected brass is now ready for full-length sizing, decapping and re-priming. Historically, primer crimps on GI brass have caused some head-scratching (and vile language) among handloaders. Our next installment will detail efficient, easy and practical methods to remove primer crimp, plus other useful handloading tips. Until next week, Good Shooting!
NOTE: The USAMU Handloading (HL) Shop does not RE-load fired 5.56 brass. We use virgin LC brass with our chosen primer already staked in place. However, our staff has extensive personal experience reloading GI brass for competition, which will supplement the Shop’s customary steps. In handloading, as in life, there are many ways to accomplish any given task. Our suggestions are note presented as the “only way,” by any means. Time for loading/practicing is always at a premium. Readers who have more efficient, alternative methods that maintain top accuracy are invited to share them here.
Accuracy Potential of Mil-Surp 5.56×45 Brass
So, how accurate can previously-fired GI surplus brass be in a good National Match AR-15? Well, here’s a data point from many years ago that might be of interest. A High Power shooter who wrote for the late Precision Shooting magazine took a Bill Wylde-built AR match rifle to a registered Benchrest match. His first 5-round group ever fired in a BR match was officially measured at 0.231″ at 200 hundred yards. This was fired in front of witnesses, while using a moving target backer that confirmed all five rounds were fired.
He recounted that his ammo was loaded progressively with factory 52gr match bullets and a spherical powder using mixed years of LC brass with no special preparation whatsoever. Obviously, this was “exceptional”. However, he had no difficulty obtaining consistent 0.5-0.6 MOA accuracy at 200 yards using LC brass and a generic “practice” load that was not tuned to his rifle.
Saving Money by Using GI Brass
So, with good commercial brass readily available, why would one go to all the extra steps necessary to process fired GI brass? [Editor: It’s about saving money.]
Economically, it makes great sense. When the author was actively practicing and competing with the service rifle, he had ~3,000 rounds of 5.56mm brass, which allowed him to load during winter and spend most time in the summer practicing. If one were wealthy and wanted to shoot nothing but the finest imported brass, the current cost of 3,000 is ~$1920 (plus shipping.)
Dropping down to good, but less-expensive new, U.S. commercial brass brings the price to a much more realistic ~$720. However, at current rates, the same amount of surplus GI once-fired brass costs between $120 — $150, leaving lots of room in the budget for other expenses. [Editor: that’s less than 10% of the cost of the best imported brass.]
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AR-15 Cartridge line-up image from 80% Arms, used with permission. This selection omits our favorite alternative — the 20 Practical (.223 Rem necked down to .204 Caliber).
Instead of using the standard .223 Remington or 5.56x45mm NATO round, you have many options for an AR-15, as shown above. This photo is from Complete Guide to Alternative AR-15 Rounds in the 80% Arms Blog. Some of the most notable alternative chamberings for AR-15s are:
20 Practical — Simply the .223 Rem necked down to .204 caliber. Requires new barrel. Same bolt, same magazines. Best Bang for the Buck. 6.5 Grendel — Moderately expensive, 6.5 Grendel requires a new barrel, bolt, and magazines. Most use the 6.5 Grendel for competitive shooting and/or hunting. .300 Blackout — Moderately expensive, the .300 Blackout requires a barrel change. This is used for home defense, and hunting. WARNING — with some bullets this round can be chambered in a .223 Rem barrel, with disastrous consequences. .458 SOCOM — Pretty expensive, requires new barrel and bolt. The .458 SOCOM round is typically used for hunting though it was originally designed for Close Quarters Battle (CQB). .50 Beowulf — The most expensive alternative AR-15 cartridge, this requires new barrel and bolt. The .50 Beowulf was created for game hunting, but most hunters use something more practical.
Of these five options, our top choice is the 20 Practical, followed by the 6.5 Grendel. Check out our featured 20 Practical AR Rifle Report. This 20 Practical cartridge is highly effective on small varmints, and has shown outstanding accuracy in AR-platform rifles crafted by Robert Whitley.
20 Practical — High-Velocity, Affordable Alternative
The 20 Practical is simply a .223 Remington necked down to .204 caliber. This efficient little cartridge can launch 32-grainers at over 4200 fps, with impressive results on P-Dogs. This makes the 20 Practical a great choice for an AR-based varmint rifle.
20 Practical Ultimate Varminter
A decade ago, as a “proof-of-concept”, AccurateShooter.com created a 20 Practical AR15 Ultimate Varminter with a custom 20-caliber upper from Robert Whitley of AR-X Enterprises, LLC. That project rifle was ultra-accurate — every 5-shot group out of the gun was less than the size of a dime. That gun was auctioned off, but Robert Whitley continues to produce custom 20 Practical AR15 uppers. (The 20 Practical cartridge is simply the .223 Rem necked down to 20 caliber — you can use standard .223 brass and load with standard .223 Rem dies. Just swap in a smaller expander and use smaller neck bushings.)
The 6.5 Grendel — Accurate, Plus Good for Hunters
The 6.5 Grendel round is one of the most accurate cartridges for the AR-15 platform. The 6.5 Grendel round offers a larger-diameter, .264-caliber (6.5mm) bullet running at good velocities. This provides ample energy for smaller game and deer. The 6.5 Grendel is often used for hunting deer up to 300 yards.
History of the 6.5 Grendel Cartridge
The 6.5 Grendel originated as a 6mm PPC necked up to 6.5 mm. After Alexander Arms relinquished the “6.5 Grendel” Trademark, the 6.5 Grendel was standardized as an official SAAMI cartridge. It has become popular with target shooters and hunters alike because it is accurate, efficient, and offers modest recoil. Good for small to medium game, the 6.5 Grendel is becoming a popular chambering in lightweight hunting rifles, such as the Howa 1500 Youth Model.
The .300 Blackout — Risky Business
The .300 Blackout appeals to folks who want a .30-caliber defense round. This can be loaded at various velocities. Loaded at subsonic speeds and shot with a suppressor, the .300 BLK offers very low sound levels. Unfortunately, that .300 Blackout cartridge can fit in a .223 Rem chamber. Shooting a .308-caliber bullet in .223 bore is a recipe for disaster.
The .300 AAC Blackout aka “300 BLK”, is a compact 30-caliber cartridge designed to work in AR-15 rifles. It has a shorter cartridge case to accommodate the bigger 30-caliber bullet while still fitting in a standard AR-15 magazine. Unfortunately, that’s the danger. A careless shooter can toss a .300 Blackout cartridge in with .223 Rem rounds without noting. And because the case-head size is the same as the .223 Rem (5.56×45) the rifle’s bolt assembly will happily chamber and fire the .300 BLK round. Problem is, that forces a .308 diameter bullet down an undersized .223-caliber bore. Not good!
This images were provided by Tactical Rifle Shooters on Facebook. The message was clear: “Don’t try to run 300 Blackout in your .223/5.56mm. It won’t end well. The problem is identical rifles and identical magazines but different calibers.”
Image from Accurate Shooter Forum. Cutaway shows the jammed .30-Cal bullet:
For those who MUST have a .300 Blackout, here are some things you can do:
1. Use different colored magazines for .300 Blackout vs. .223 Remington.
2. Mark .223 Rem upper handguards with the caliber in bright paint.
2. Fit all your uppers with caliber-labeled ejection port covers.
4. Mark all .300 BLK Rounds with heavy black marker.
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With ammunition in short supply these days, we know ammo production is on people’s minds. Top industry leaders have said the USA will face ammo shortages well into 2021. So ammo-makers big and small are ramping up production to meet demand. If you’re curious how ammunition is created on the assembly by a relatively small, speciality manufacturer, watch the video below to see the entire process, start to finish.
This video from Fog Ammunition reveals how .223 Rem ammo is made. Starting with boxes of bullets and bags of cartridge brass, this video shows how components are bulk-sorted, then .223 Rem ammunition is produced on a modern, linear multi-stage loading machine. In assembly-line fashion, cases are primed, powder is added, bullets are placed, final seating depth is set, and then the case is crimped.
If you’ve never seen an automated loader in action you should definitely watch this video. With this kind of machine, a new round is produced every second or so (see video 1:15 to 1:55). The .223 Remington ammunition featured in this video is loaded with Sierra BlitzKing bullets. Fog offers both rifle and pistol ammo loaded with quality components.
Video Shows Automated Loading Process Start to Finish (Worth Watching):
Remember when primers were plentiful and priced affordably?
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Probably the most popular centerfire rifle round in the Western Hemisphere is the .223 Remington and its metric match, the 5.56x45mm. Though many folks use “.223 Rem” and “5.56×45″ interchangeably, there are some meaningful differences in specifications for the original .223 Rem and the 5.56x45mm cartridge, as adopted by the U.S. military and NATO armies. The default chamber throats are slightly different and the .223 Rem is rated at 55,000 PSI vs. 62,366 PSI for the 5.56x45mm.*
.223 Rem vs 5.56x45mm — Key Differences
There is a truly outstanding, very thorough article on the subject, published by LuckyGunner.com.** This involved extensive testing, with pressure monitors, of 5.56x45mm ammo in .223 Rem chambers. Those tests revealed the peak pressures. Here is one of the ammo test charts:
NOTE: “The observed chamber pressure for Federal XM855 5.56mm ammunition in a .223 Rem chamber exceeded .223 maximum pressures, but not by a massive amount. The ninth shot (the red line) was an underpowered cartridge which exhibited significantly lower velocity and pressure than the other rounds, so it was excluded from the average velocity and pressure numbers for this chamber.”
And if you’re curious, LuckyGunner also fired .223 Rem ammo in a 5.56x45mm NATO-chambered AR15 rifle. As you would expect, the peak pressures were significantly lower, but the .223 Rem ammo still cycled the semi-auto AR-platform rifle perfectly well:
UltimateReloader.com Explains .223 Rem vs. 5.56x45mm
To explain the key differences between the .223 Rem and 5.56x45mm cartridges our friend Gavin Gear of UltimateReloader.com has created a very thorough 12-minute video. This covers the cartridge specifications and explains key considerations for hand-loaders. Gavin also addresses the oft-asked question “Can I shoot 5.56x45mm ammo in my .223 Rem chamber?” Gavin’s video is definitely worth watching. In fact, this is one of the most popular videos Gavin has ever created — it has been watched over 300,000 times on YouTube.
What Exactly Is the 5.56x45mm NATO Cartridge?
The 5.56×45mm NATO is a rimless bottle-necked intermediate cartridge family standardized by NATO with development work by FN Herstal. It consists of the SS109, SS110, and SS111 cartridges. Under STANAG 4172, it is a standard cartridge for NATO forces as well as many non-NATO countries.
Bullet diameter: 5.70 mm (0.224 in)
Maximum pressure (EPVAT): 430.00 MPa (62,366 psi)
Maximum pressure (SCATP 5.56): 380.00 MPa (55,114 psi)
Case length: 44.70 mm (1.760 in)
Rifling twist: 178 mm or 229 mm (1 in 7 in)
Parent case: .223 Remington (M193)
Ammo-Maker Federal Premium Compares .223 Rem and 5.56x45mm
Here is a video from ammo-maker Federal Premium explaining the difference between .223 Remington and 5.56x45mm NATO. Federal states that you may experience excessive pressures when firing a 5.56x45mm in a standard .223 Remington chamber:
One leading gunwriter has addressed the question of shooting 5.56x45mm ammo in .223 Rem chambers. He advocates caution (for more info, SEE pressure tests by LuckyGunner.com):
“I have received a slew of questions — many from first time AR-type rifle buyers — about the .223 Rem and the 5.56×45 mm NATO cartridges. Can I shoot 5.56×45 mm NATO in my .223 and vice-versa? Are these the same cartridge?
Externally, the two cartridge cases are identical. The main differences are that 5.56×45 mm NATO operates at a higher chamber pressure (about 60,000 PSI versus 55,000 PSI on the .223 Rem.) and the 5.56’s chamber is slightly larger than that of the .223 Rem. Also, the throat or leade is longer in the 5.56×45 mm chamber. What does this mean? You should not shoot 5.56×45 mm NATO out of a rifle that is chambered in .223 Rem. And be aware that some .223 Rem. ammunition will not reliably cycle through some AR-style .223 Rem. rifles, but it usually does. As a matter of fact, I have not encountered any difficulty with current .223 Rem. loads cycling through a 5.56 mm AR-style rifle.” – Mark Keefe, Editor, American Rifleman
* According to the official NATO proofing guidelines, the 5.56×45mm NATO case can handle up to 430.0 MPa (62,366 psi) piezo service pressure. The U.S. SAAMI lists Maximum Average Pressure (MAP) for the .223 Remington cartridge as 55,000 psi (379.2 MPa) piezo pressure with deviation of up to 58,000 psi (399.9 MPa). The chamber for military 5.56×45mm NATO has a longer throat prior to the bullet contacting the rifling which results in lower pressures when firing 5.56×45mm NATO ammunition. If 5.56×45mm NATO is used in rifles chambered for .223 Remington the bullet will be engraving the rifling when chambered. which can increase pressures past SAAMI Max levels. NOTE: The C.I.P. standards for the C.I.P. civilian .223 Remington chamber are much closer to the military 5.56×45mm NATO chamber.
** The full-length LuckyGunner article is well worth reading. It even provides specifications for a number of .223 Rem reamer types, and compares the original .223 Rem, the 5.56x45mm NATO, and the modern .223 Wylde chamberings.
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Each Wednesday, the U.S. Army Marksmanship Unit publishes a reloading “how-to” article on the USAMU Facebook page. A recent “Handloading Hump Day” post covered preparation of once-fired 5.56x45mm brass. This article, the first in a 3-part series, has many useful tips. If you shoot a rifle chambered in .223 Rem or 5.56x45mm, this article is worth reading.
This week, Handloading Hump-Day will answer a special request from several competitive shooters who asked about procedures for morphing once-fired GI 5.56mm brass into accurate match brass for NRA High Power Rifle use. The USAMU has used virgin Lake City (LC) 5.56 brass to win National Championships and set National Records for many years. In this 3-part series, we’ll share techniques proven to wring match-winning accuracy from combat-grade brass.
GI brass has an excellent attribute, worth noting — it is virtually indestructible. Due to its NATO-spec hardness, the primer pockets last much longer than most commercial brass when using loads at appropriate pressures.
Preparing Once-Fired GI 5.56 Brass for Reloading (Part 1 of 3)
Assuming our readers will be getting brass once-fired as received from surplus dealers, the following steps can help process the low-cost raw material into reliably accurate components.
1. Clean the Brass
First, clean the brass of any dirt/mud/debris, if applicable. Depending on the brass’s condition, washing it in a soap solution followed by a thorough rinsing may help. [This step also extends the life of the tumbling media.] Approaches range from low-tech, using gallon jugs 1/2 full of water/dish soap plus brass and shaking vigorously, to more high-tech, expensive and time-consuming methods.
2. Wet-Tumbling Options (Be Sure to Dry the Brass)
When applying the final cleaning/polish, some use tumblers with liquid cleaning media and stainless steel pins for a brilliant shine inside and out, while others take the traditional vibratory tumbler/ground media approach. Degree of case shine is purely personal preference, but the key issue is simple cleanliness to avoid scratching ones’ dies.
If a liquid cleaner is used, be SURE to dry the cases thoroughly to preclude corrosion inside. One method is to dump the wet brass into an old pillow case, then tilt it left/right so the cases re-orient themselves while shifting from corner to corner. Several repetitions, pausing at each corner until water stops draining, will remove most water. They can then be left to air-dry on a towel, or can be dried in a warm (150° F-200° F max) oven for a few minutes to speed evaporation.
Shown below are Lake City cases after cleaning with Stainless Media (STM). Note: STM Case cleaning was done by a third party, not the USAMU, which does not endorse any particular cleaning method.
3. Inspect Every Case
Once dry, inspect each case for significant deformation (i.e., someone stepped on it), damaged mouths/necks and case head/rim damage. Some rifles’ ejectors actually dig small chunks of brass out of the case head — obviously, not ideal for precision shooting. Similarly, some extractors can bend the case rims so badly that distortion is visible when spinning them in one’s fingers. These can be used for plinking, but our match brass should have straight, undamaged rims.
Dented case mouths are common, and these can easily be rounded using a conical, tapered tool, [such as a .223 expander mandrel. A dummy 7.62 or .30-06 cartridge with a FMJ spitzer can also work.] If most of your brass is of one headstamp, this is a good time to cull out any odd cases.
4. Check the Primers Before Decapping
Your clean, dry and inspected brass is now ready for full-length sizing, decapping and re-priming. Historically, primer crimps on GI brass have caused some head-scratching (and vile language) among handloaders. Our next installment will detail efficient, easy and practical methods to remove primer crimp, plus other useful handloading tips. Until next week, Good Shooting!
NOTE: The USAMU Handloading (HL) Shop does not RE-load fired 5.56 brass. We use virgin LC brass with our chosen primer already staked in place. However, our staff has extensive personal experience reloading GI brass for competition, which will supplement the Shop’s customary steps. In handloading, as in life, there are many ways to accomplish any given task. Our suggestions are note presented as the “only way,” by any means. Time for loading/practicing is always at a premium. Readers who have more efficient, alternative methods that maintain top accuracy are invited to share them here.
Accuracy Potential of Mil-Surp 5.56×45 Brass
So, how accurate can previously-fired GI surplus brass be in a good National Match AR-15? Well, here’s a data point from many years ago that might be of interest. A High Power shooter who wrote for the late Precision Shooting magazine took a Bill Wylde-built AR match rifle to a registered Benchrest match. His first 5-round group ever fired in a BR match was officially measured at 0.231″ at 200 hundred yards. This was fired in front of witnesses, while using a moving target backer that confirmed all five rounds were fired.
He recounted that his ammo was loaded progressively with factory 52gr match bullets and a spherical powder using mixed years of LC brass with no special preparation whatsoever. Obviously, this was “exceptional”. However, he had no difficulty obtaining consistent 0.5-0.6 MOA accuracy at 200 yards using LC brass and a generic “practice” load that was not tuned to his rifle.
Saving Money by Using GI Brass
So, with good commercial brass readily available, why would one go to all the extra steps necessary to process fired GI brass? [Editor: It’s about saving money.]
Economically, it makes great sense. When the author was actively practicing and competing with the service rifle, he had ~3,000 rounds of 5.56mm brass, which allowed him to load during winter and spend most time in the summer practicing. If one were wealthy and wanted to shoot nothing but the finest imported brass, the current cost of 3,000 is ~$1920 (plus shipping.)
Dropping down to good, but less-expensive new, U.S. commercial brass brings the price to a much more realistic ~$720. However, at current rates, the same amount of surplus GI once-fired brass costs between $120 — $150, leaving lots of room in the budget for other expenses. [Editor: that’s less than 10% of the cost of the best imported brass.]
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Probably the most popular centerfire rifle round in the Western Hemisphere is the .223 Remington and its metric match, the 5.56x45mm. Though many folks use “.223 Rem” and “5.56×45″ interchangeably, there are some meaningful differences in specifications for the original .223 Rem and the 5.56x45mm cartridge, as adopted by the U.S. military and NATO armies. The default chamber throats are slightly different and the .223 Rem is rated at 55,000 PSI vs. 62,366 PSI for the 5.56x45mm.*
.223 Rem vs 5.56x45mm — Key Differences
There is a truly outstanding, very thorough article on the subject, published by LuckyGunner.com.** This involved extensive testing, with pressure monitors, of 5.56x45mm ammo in .223 Rem chambers. Those tests revealed the peak pressures. Here is one of the ammo test charts:
NOTE: “The observed chamber pressure for Federal XM855 5.56mm ammunition in a .223 Rem chamber exceeded .223 maximum pressures, but not by a massive amount. The ninth shot (the red line) was an underpowered cartridge which exhibited significantly lower velocity and pressure than the other rounds, so it was excluded from the average velocity and pressure numbers for this chamber.”
And if you’re curious, LuckyGunner also fired .223 Rem ammo in a 5.56x45mm NATO-chambered AR15 rifle. As you would expect, the peak pressures were significantly lower, but the .223 Rem ammo still cycled the semi-auto AR-platform rifle perfectly well:
UltimateReloader.com Explains .223 Rem vs. 5.56x45mm
To explain the key differences between the .223 Rem and 5.56x45mm cartridges our friend Gavin Gear of UltimateReloader.com has created a very thorough 12-minute video. This covers the cartridge specifications and explains key considerations for hand-loaders. Gavin also addresses the oft-asked question “Can I shoot 5.56x45mm ammo in my .223 Rem chamber?” Gavin’s video is definitely worth watching. In fact, this is one of the most popular videos Gavin has ever created — it has been watched over 300,000 times on YouTube.
What Exactly Is the 5.56x45mm NATO Cartridge?
The 5.56×45mm NATO is a rimless bottle-necked intermediate cartridge family standardized by NATO with development work by FN Herstal. It consists of the SS109, SS110, and SS111 cartridges. Under STANAG 4172, it is a standard cartridge for NATO forces as well as many non-NATO countries.
Bullet diameter: 5.70 mm (0.224 in)
Maximum pressure (EPVAT): 430.00 MPa (62,366 psi)
Maximum pressure (SCATP 5.56): 380.00 MPa (55,114 psi)
Case length: 44.70 mm (1.760 in)
Rifling twist: 178 mm or 229 mm (1 in 7 in)
Parent case: .223 Remington (M193)
Ammo-Maker Federal Premium Compares .223 Rem and 5.56x45mm
Here is a video from ammo-maker Federal Premium explaining the difference between .223 Remington and 5.56x45mm NATO. Federal states that you may experience excessive pressures when firing a 5.56x45mm in a standard .223 Remington chamber:
One leading gunwriter has addressed the question of shooting 5.56x45mm ammo in .223 Rem chambers. He advocates caution (for more info, SEE pressure tests by LuckyGunner.com):
“I have received a slew of questions — many from first time AR-type rifle buyers — about the .223 Rem and the 5.56×45 mm NATO cartridges. Can I shoot 5.56×45 mm NATO in my .223 and vice-versa? Are these the same cartridge?
Externally, the two cartridge cases are identical. The main differences are that 5.56×45 mm NATO operates at a higher chamber pressure (about 60,000 PSI versus 55,000 PSI on the .223 Rem.) and the 5.56’s chamber is slightly larger than that of the .223 Rem. Also, the throat or leade is longer in the 5.56×45 mm chamber. What does this mean? You should not shoot 5.56×45 mm NATO out of a rifle that is chambered in .223 Rem. And be aware that some .223 Rem. ammunition will not reliably cycle through some AR-style .223 Rem. rifles, but it usually does. As a matter of fact, I have not encountered any difficulty with current .223 Rem. loads cycling through a 5.56 mm AR-style rifle.” – Mark Keefe, Editor, American Rifleman
* According to the official NATO proofing guidelines, the 5.56×45mm NATO case can handle up to 430.0 MPa (62,366 psi) piezo service pressure. The U.S. SAAMI lists Maximum Average Pressure (MAP) for the .223 Remington cartridge as 55,000 psi (379.2 MPa) piezo pressure with deviation of up to 58,000 psi (399.9 MPa). The chamber for military 5.56×45mm NATO has a longer throat prior to the bullet contacting the rifling which results in lower pressures when firing 5.56×45mm NATO ammunition. If 5.56×45mm NATO is used in rifles chambered for .223 Remington the bullet will be engraving the rifling when chambered. which can increase pressures past SAAMI Max levels. NOTE: The C.I.P. standards for the C.I.P. civilian .223 Remington chamber are much closer to the military 5.56×45mm NATO chamber.
** The full-length LuckyGunner article is well worth reading. It even provides specifications for a number of .223 Rem reamer types, and compares the original .223 Rem, the 5.56x45mm NATO, and the modern .223 Wylde chamberings.
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Displayed are results with Federal Gold Medal Match — quite impressive accuracy!
Criterion Barrels has published an interesting Ammo Comparison Test, shooting seven (7) different varieties of .223 Rem ammunition out of an AR15 fitted with Criterion Barrel. Each ammo type was chronographed (10-shot string), then five-shot groups were shot at 100 yards. Along with handloads (69gr Sierra MK + Varget), six (6) types of commercial ammo were tested:
PREMIUM Type Ammo:
Federal Gold Medal Match (69gr SMK)
Creedmoor 75gr HPBT
Prime 77gr OTM (Open Tip Match)
BULK Type Ammo:
Federal American Eagle XM193 (55gr FMJ)
Wolf Gold (55gr FMJ)
Wolf Polyformance Steel Case (55gr FMJ)
Here are the results for the four best commercial ammo types tested: Federal Gold Medal Match (GMM) with 69gr SMK, Prime 77gr OTM, Creedmoor 75gr HPBT, and American Eagle XM193 (55gr FMJ). The Gold Medal Match shot the best of all factory ammo tested. In fact, the GMM even shot slightly better than the handloads, which averaged 0.79″ for the three accurized groups.
The results are quite interesting. The Federal GMM actually shot the best, beating “untailored” handloads. Basic accurizing efforts and a much better rest set-up showed significant benefits with most ammo types (but not the bulk Wolf Ammo). As you would expect, the more expensive ammo shot best: “Chart 1.2 [below] showcases the average [after accurizing] five-round group sizes with each type of ammunition at 100 yards, while Chart 1.3 lists the price per round of each ammunition type. It becomes immediately evident by reviewing these two graphs that there is an inverse relationship between group size and factory ammunition price.”
Accurizing Improvements — Better Scope, Better Rests, Accu-Wedge
As you would expect, some basic accurizing efforts improved accuracy with the better ammo. The accurizing process included: 1) Swapping to a Vortex Viper PST Gen 1 6-24x50mm optic; 2) Adding an Accu-Wedge; 3) Improving fitment during reassembly, and 4) Switching from Harris bipod to a Sinclair Front Rest and Edgewood rear bag for added stability. The same 1:8″-twist Criterion barrel was used throughout the testing process.
If you shoot an AR15, or even shoot a .223 Rem bolt gun with factory ammo, you should probably read this test in full. Criterion put a lot of time into the testing, and experimented with a variety of AR options showcased in a series of YouTube videos. SEE: Accurizing the AR-15 Video Playlist.
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Many visitors to the site ask us, “I’ve got a .223 and .308. What will a 6mmBR Norma (6BR) give me that I’m not getting already?” Well first you will probably average consistently smaller groups than your current .223 or .308 rifle (assuming the 6BR has a quality barrel and trigger). A good .308 Winchester can be superbly accurate, no question about that, but the lesser recoil of the 6BR works in the shooter’s favor over a long string of fire. Even with a Rem 700 or Savage action factory action, a 6BR with a benchrest stock, premium barrel, and a high-quality chambering job should deliver 5-shot groups in the high twos to mid-threes, provided you do your job. We have one 6BR rifle that shoots Lapua factory-loaded 6BR ammunition in the low twos and high ones. That’s exceptional, we admit, but it still shows how the 6BR is an inherently accurate cartridge, even with factory loads.
20 Practical Ultimate Varminter
The 
