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. 6mm ARC — The 6mm ARC (from Hornady), is a SAAMI cartridge optimized for AR-platform rifles. The 6mm ARC is basically a 6.5 Grendel necked down to 6mm, with the shoulder moved back around .030″. 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. .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
Many years back, 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. 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.
20 Practical in AR15 Demonstration Video
6mm ARC — Popular New SAAMI Cartridge Promoted by Hornady
The 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 magazines designed for 6.5 Grendel.
While 6-6.5 Grendel shooters are known to run stout pressures, the 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 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.
Share the post "Beyond the .223 Rem — Alternative AR-15 Cartridge Types"
Yet another .300 Blackout disaster. 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 Rem.
2. Fit all your uppers with caliber-labeled ejection port covers.
3. Mark .223 Rem upper handguards with the caliber in bright paint.
4. Mark all .300 BLK Rounds with heavy black marker.
Comments by Folks Who Viewed these .300 Blackout Disaster Photos:
“The .300 Blackout is simply a badly-designed round. A properly-designed round would have had a feature in the shape that would have prevented cross loading in the first place.” — D. Santiago
“I almost made that mistake… I had a magazine of 300 BLK inserted in my .223/5.56 all night. Fortunately, I never pulled the trigger. Once I realized the mistake, I almost got ill. [After that incident] I no longer own a 300 BLK.” — B. Welch
“Happened to me hog hunting from a helo. Gun exploded in my face.” — B. Hood
“Fire-forming projectiles [is] so wrong in centerfire!” — M. Stres
“Had some dude come into the store the other day wanting .300 Blackout ammo to shoot in his 5.56 AR. It took 15 minutes of explaining for him to understand you got to have a .300 Blackout Upper!” — R. Williams
Share the post "Devastating Disaster from .300 Blackout in .223 Rem Rifle"
Yet another .300 Blackout disaster. 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 Rem.
2. Fit all your uppers with caliber-labeled ejection port covers.
3. Mark .223 Rem upper handguards with the caliber in bright paint.
4. Mark all .300 BLK Rounds with heavy black marker.
Comments by Folks Who Viewed these .300 Blackout Disaster Photos:
“The .300 Blackout is simply a badly-designed round. A properly-designed round would have had a feature in the shape that would have prevented cross loading in the first place.” — D. Santiago
“I almost made that mistake… I had a magazine of 300 BLK inserted in my .223/5.56 all night. Fortunately, I never pulled the trigger. Once I realized the mistake, I almost got ill. [After that incident] I no longer own a 300 BLK.” — B. Welch
“Happened to me hog hunting from a helo. Gun exploded in my face.” — B. Hood
“Fire-forming projectiles [is] so wrong in centerfire!” — M. Stres
“Had some dude come into the store the other day wanting .300 Blackout ammo to shoot in his 5.56 AR. It took 15 minutes of explaining for him to understand you got to have a .300 Blackout Upper!” — R. Williams
Share the post ".300 Blackout Fired in .223 Rem AR — Recipe for Disaster"
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.
Share the post "Sunday GunDay: Beyond .223 Rem — Alternative AR Cartridges"
Photos and Facebook post by Tactical Rifle Shooters
Yet another .300 Blackout disaster. 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 Rem.
2. Fit all your uppers with caliber-labeled ejection port covers.
3. Mark .223 Rem upper handguards with the caliber in bright paint.
4. Mark all .300 BLK Rounds with heavy black marker.
Comments by Folks Who Viewed these .300 Blackout Disaster Photos:
“The .300 Blackout is simply a badly-designed round. A properly-designed round would have had a feature in the shape that would have prevented cross loading in the first place.” — D. Santiago
“I almost made that mistake… I had a magazine of 300 BLK inserted in my .223/5.56 all night. Fortunately, I never pulled the trigger. Once I realized the mistake, I almost got ill. [After that incident] I no longer own a 300 BLK.” — B. Welch
“Happened to me hog hunting from a helo. Gun exploded in my face.” — B. Hood
“Fire-forming projectiles [is] so wrong in centerfire!” — M. Stres
“Had some dude come into the store the other day wanting .300 Blackout ammo to shoot in his 5.56 AR. It took 15 minutes of explaining for him to understand you got to have a .300 Blackout Upper!” — R. Williams
Share the post ".300 Blackout Round in .223 Rem AR Upper — Instant Disaster"
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.
Share the post "Beyond .223 Rem — The Many Alternative AR Chamberings"
Photos and Facebook post by Tactical Rifle Shooters
Yet another .300 Blackout disaster. 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 Rem.
2. Fit all your uppers with caliber-labeled ejection port covers.
3. Mark .223 Rem upper handguards with the caliber in bright paint.
4. Mark all .300 BLK Rounds with heavy black marker.
Comments by Folks Who Viewed these .300 Blackout Disaster Photos:
“The .300 Blackout is simply a badly-designed round. A properly-designed round would have had a feature in the shape that would have prevented cross loading in the first place.” — D. Santiago
“I almost made that mistake… I had a magazine of 300 BLK inserted in my .223/5.56 all night. Fortunately, I never pulled the trigger. Once I realized the mistake, I almost got ill. [After that incident] I no longer own a 300 BLK.” — B. Welch
“Happened to me hog hunting from a helo. Gun exploded in my face.” — B. Hood
“Fire-forming projectiles [is] so wrong in centerfire!” — M. Stres
“Had some dude come into the store the other day wanting .300 Blackout ammo to shoot in his 5.56 AR. It took 15 minutes of explaining for him to understand you got to have a .300 Blackout Upper!” — R. Williams
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Yet another .300 Blackout disaster. 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.”
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 Rem.
2. Fit all your uppers with caliber-labeled ejection port covers.
3. Mark .223 Rem upper handguards with the caliber in bright paint.
4. Mark all .300 BLK Rounds with heavy black marker.
Comments by Folks Who Viewed these .300 Blackout Disaster Photos:
“The .300 Blackout is simply a badly-designed round. A properly-designed round would have had a feature in the shape that would have prevented cross loading in the first place.” — D. Santiago
“I almost made that mistake… I had a magazine of 300 BLK inserted in my .223/5.56 all night. Fortunately, I never pulled the trigger. Once I realized the mistake, I almost got ill. [After that incident] I no longer own a 300 BLK.” — B. Welch
“Happened to me hog hunting from a helo. Gun exploded in my face.” — B. Hood
“Fire-forming projectiles [is] so wrong in centerfire!” — M. Stres
“Had some dude come into the store the other day wanting .300 Blackout ammo to shoot in his 5.56 AR. It took 15 minutes of explaining for him to understand you got to have a .300 Blackout Upper!” — R. Williams
Share the post "Scary Stuff — .300 Blackout Fired in a .223 Rem Barrel"
Every year we anxiously await the new product announcement from Lapua. In 2014, Lapua brought out new bullets and new cartridge brass — .221 Fireball and .50 BMG. For 2015, Lapua once again brings out new brass offerings, this time three new flavors of cartridge brass, all made to Lapua’s exacting standards. First, Lapua will introduce factory 300 AAC Blackout (300 BLK) brass. This promises to take this highly-efficient, AR-friendly .30-caliber cartridge to another accuracy level. Second, Lapua will offer premium brass for the 7mm-08 cartridge, a very popular round among hunters and silhouette shooters. Lastly, in 2015, Lapua will produce 8x57mm JS brass. That’s good news for fans of this classic Mauser cartridge.
300 AAC Blackout Brass
Lapua’s Press release states: “Few cartridges have generated as much immediate interest as the 300 Blackout. Standardized by AAC, this diminutive cartridge is derived from the 223 Remington. Intended specifically for use in suppressed firearms, the versatility of the Blackout has appealed to a much broader range of shooters than just the audience for which it was originally designed. [Originally] intended to drive 220 grain bullets at subsonic velocities, the switch to lightweight bullets such as the 125 grain offerings delivers performance very similar to the venerable 7.62×39 cartridge. This makes the 300 Blackout potent enough for a wide range of shooting tasks, from certain tactical applications to many short range hunting situations involving medium-sized game. The ability for many 5.56mm/223 systems to be switched over to the 300 Blackout, merely by changing barrels, makes this an incredibly versatile combination. Lapua brings over nine decades of case manufacturing knowledge, precision and quality to the new Blackout, assuring the shooter of the very best performance.”
7mm-08 Remington Brass
Lapua notes that it’s new 7mm-08 brass is made to very high standards, benefiting hunters as well as competitors: “The 7mm-08 came to dominate the High Power Silhouette rifle game shortly after its introduction, offering a superb combination of power, light recoil and accuracy. Since then, it has also been used to win National Championships in High Power competition, and become a staple for hunters as well. With ballistic performance exceeding that of the time honored 7x57mm Mauser, but suited to a shorter action, the 7mm-08 is an ideal cartridge for most big game hunting. Lapua brings… state-of-the-art manufacturing methods, combined with old world craftsmanship, to the production of these cases. Primer pockets and flash holes are held to strict tolerances to withstand repeated firings and reloadings. After final necking of the case, they are finished with the proper anneal [for] accuracy and durability.” Lapua also notes that it offers two new 7mm Scenar bullets, which will work very well in the new 7mm-08 cartridge brass.
8x57mm JS Brass
Last but not least, Lapua is producing 8x57mm JS brass. Lapua notes that: “When the 8x57mm JS cartridge was introduced in 1905, its innovative use of a high velocity and relatively light weight pointed bullet design revolutionized infantry combat. An outgrowth on the original 8x57J military round, the 8x57mm JS round served the German military in both world wars, and became a popular sporting cartridge in any area where there was a strong German influence. From African plains game to European stag and boar, the 8mm Mauser has earned an enviable reputation as a big game round in a wide array of conditions. Accurate, versatile and powerful, the 8x57mm JS still serves the sporting community well for a host of hunting applications. In answer to the requests of the many devotees of this fine cartridge, Lapua is pleased to announce our introduction of the new 8x57mmJS case. The new 8x57mmJS will deliver the same accurate, reliable performance for which Lapua cases are world renowned. This means tough, durable cases that will not only withstand repeated loadings, but retain their accuracy shot after shot. [Lapua’s 8x57mm JS brass offers] very tight tolerances in neck wall concentricity and overall uniformity.”
See Lapua’s New Products at SHOT Show 2015
If you plan to attend SHOT Show in Las Vegas, stop by and visit the Lapua Exhibit (booth #11929). With luck, samples of the new 7mm-08, 300 BLK, and 8×57 JS brass will be available to view. Lapua engineers will be on hand to talk about Lapua brass and bullets, and explain the production processes that make Lapua brass so durable and consistent. In recent years, in the world of centerfire competition, Lapua brass has absolutely dominated the winner’s circles as well as the record-books.
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Robert Whitley of AR-X Enterprises has a new .30-caliber cartridge for AR-platform rifles. The new 30 ARX is based on the 6.5 Grendel parent case necked-up to .30 caliber. The 30 ARX mag-feeds flawlessly in an AR15, while offering excellent accuracy, good velocity, and serious knock-down power. Compared to a 300 AAC Blackout (300 BLK), the new 30 ARX holds much more powder so it can push bullets faster and harder. Whitley’s 30 ARX boasts 57% more case capacity than a 300 Blackout. As a result, the 30 ARX outperforms the 300 BLK by a large margin. In a 20″-barreled AR, the 30 ARX can drive a 125gr bullet at 2500+ fps, or launch a heavier 150gr bullet at 2400+ fps:
30 ARX Loads
H4198, CCI BR4 Primers,
Necked-up Lapua 6.5 Grendel Brass:
2419 FPS: 28.0 gr. H4198, Nosler 125gr Ballistic Tip Hunting Bullet (2.260″ OAL)
2517 FPS: 29.0 gr. H4198, Nosler 125gr Ballistic Tip Hunting Bullet (2.260″ OAL)
2363 FPS: 28.0 gr. H4198, Sierra 150gr BT Hunting Bullet (2.240″ OAL)
2441 FPS: 29.0 gr. H4198, Sierra 150gr BT Hunting Bullet (2.240″ OAL)
Robert Whitley explains the advantanges of the 30 ARX for AR-platform rifles: “The 30 ARX is a cartridge designed from the get-go for use in an AR-15. The case length and chamber design of the 30 ARX are optimal. The case allows the use of many of the favorite .30-cal bullets, magazine fed out of an AR-15 and backed by some real power. Brass is easy to make with a simple necking-up process. Neck it up, load it and go shoot. Good 6.5 Grendel brass is readily available, and we have 30 ARX dies available.”
Watch One-Step Process for Forming 30 ARX Case from 6.5 Grendel Brass
With the ability of Lapua 6.5 Grendel brass to handle stout loads, the 30 ARX cartridge delivers 30-30 Winchester-class performance, from the modern, semi-auto AR-15 platform. The 30 ARX cartridge has sufficient case capacity to push popular .30-cal bullets fast and accurately even at moderate chamber pressures. The case has approximately 38 grains water capacity. With its 57% greater capacity than a 300 Blackout, the 30 ARX is a more versatile, more powerful hunting cartridge (at least when loaded to supersonic speeds). With 150gr bullets running in the 2500 fps range, the 30 ARX offers impressive knockdown power in a cartridge that fits an AR-15 magazine.
30 ARX Cartridge OAL mag-feeds perfectly with a variety of .30-cal bullets.
Longer, heavier long-range bullets (with longer COAL) can be single-loaded.
Lapua 6.5 Grendel brass is excellent, strong brass, that is readily available.
AR-X Enterprises now offers die sets for the 30 ARX.
The neck up process is very easy. Simply lube the inside of the necks of 6.5 Grendel brass, run the brass through your re-size die (with .30 Cal expander in place).
Works well with a lot of commonly available powders such as: Hodgdon 4198, Vihtavouri N130, Accurate LT-32, Accurate AA1680.
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Lapua just dropped a bombshell — multiple bombshells, in fact. Lapua just announced that it will be producing .221 Fireball brass and .50 BMG brass starting early 2014. This will be the first truly match-grade brass ever offered for the .221 Fireball. That’s great news for varminters, who can use Lapua’s new .221 Fireball brass “as is” or neck it down to .20 Vartarg or 17 Fireball. Tactical shooters can also use the .221 Fireball brass to make the .300 Whisper and 300 Blackout sub-sonic cartridges. At the other end of the spectrum, ultra-long-range shooters now have a new ultra-premium brass source for the mighty .50 BMG. This is potentially a “game-changer” for fifty-cal shooters who have had to “make do” with military surplus brass for the most part. Lapua says the new brass, both .50 BMG and .221 Fireball, should be in the USA by early April, 2014. Sorry, no pricing info is yet available.
Here is the Lapua Product Announcement for .221 Fireball and .50 BMG Brass:
New 180-Grain and 150-Grain 7mm Scenar-L Bullets
The other big news from Lapua is the release of two new 7mm (.284 caliber) Scenar-L target bullets. Recognizing the popularity of 7mm cartridges among F-Class Open Division shooters, Lapua will offer a high-BC, 180-grain bullet. As part of the “L” series, this new 180-grainer bullet should exhibit extreme consistency in base-to-ogive measurements and bullet weight. We expect this new 180gr projectile to be extremely accurate in the .284 Winchester, .284 Shehane, 7mm WSM, and 7mm RSAUM — popular chamberings for F-Class and long-range benchrest shooters. No BC information has been released yet, but we expect the BC number to be quite high, giving this bullet great wind-bucking capability. In addition to the new 180gr 7mm Scenar-L, Lapua will offer a new 150gr 7mm bullet. This is optimized for medium range competition in Silhouette and Across-the-Course competition. It should offer great accuracy, but with less felt recoil than its 180-grain bigger brother.
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This week Student of the Gun (SOTG) heads to the range to see whether a suppressed centerfire rifle can be quieter than a rimfire rifle. SOTG tested sub-sonic .300 Blackout ammunition in an AAC Micro 7 bolt-action rifle fitted with an AAC suppressor (aka “silencer”). SOTG found that this suppressed AAC rifle, shooting sub-sonic ammo, was actually quieter than a rimfire rifle using standard velocity .22LR ammo. Watch the video below to see how the testing was done. Results are discussed at the five minute mark.
SOTG Video– Silent Shooting with the .300 Blackout
StudentoftheGun.com is a popular website that covers a variety of gun-related topics. (After the suppressor test, this week’s SOTG video includes segments on concealed carry and outdoor survival skills.) SOTG provides a full mix of content, including online videos, articles, books, and DVDs. A new video episode is uploaded every Tuesday by 6:00 pm. SOTG also offers self-defense instruction.
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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. 
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!
Lapua notes that it’s new 7mm-08 brass is made to very high standards, benefiting hunters as well as competitors: “The 7mm-08 came to dominate the High Power Silhouette rifle game shortly after its introduction, offering a superb combination of power, light recoil and accuracy. Since then, it has also been used to win National Championships in High Power competition, and become a staple for hunters as well. With ballistic performance exceeding that of the time honored 7x57mm Mauser, but suited to a shorter action, the 7mm-08 is an ideal cartridge for most big game hunting. Lapua brings… state-of-the-art manufacturing methods, combined with old world craftsmanship, to the production of these cases. Primer pockets and flash holes are held to strict tolerances to withstand repeated firings and reloadings. After final necking of the case, they are finished with the proper anneal [for] accuracy and durability.” Lapua also notes that it offers two new 7mm Scenar bullets, which will work very well in the new 7mm-08 cartridge brass.
Robert Whitley of 
This week 
