Intro: Ron Dague wanted a new gun that was similar to his trusty .223 Rem rifle, but which fired 6mm bullets. There is a superb choice of bullets in this caliber, and Ron found that the 95gr Berger VLD could be driven to a healthy 2604 FPS by the small .223 Rem case. This 6mm wildcat based on the common .223 Remington offers excellent accuracy and very low recoil — something very important in the cross-the-course discipline. In addition, Ron’s 95gr load with Alliant Reloder 15 delivered an ES of just 4 fps over ten shots. That exceptionally low ES helps achieve minimal vertical dispersion at 600 yards.
I have watched a change in thinking for NRA High Power across the course in match rifles and calibers. There are several [popular chamberings]: 6mm AR, 6.5 Grendel, 6XC, and 6.5 Creedmoor. I have seen these rifles perform and all have done very well.
When I started this project I was looking for a cartridge that shoots and feeds well from a magazine[.] I had shot the .223 Rem in my 722 Remington and knew it had fed well so I chose the .223 Remington necked up to 6mm.
The 6mm-223 gives me what I have in the standard .223 only with a better selection of bullets. I wanted a better 600-yard bullet with a higher BC than provided by the 80 and 82 grain bullets. I also wanted a 600-yard line bullet with a .500 or better B.C. for those shots that should be 10 ring or better but seem to find the 9 ring no matter how well I held and broke the shot.
Putting the 6mm-233 Project Together
My project started with ordering a 6mm barrel from Bartlein with a 1-8″ twist. I called Pacific Tool and ordered the 6mm-223 reamer. I found a used Remington 700 action at a local gun shop and already had a Remington 40X stock. I then started putting the gun together.
I already had a .223 Remington match rifle, and I wanted the 6mm-223 to be as close to the same as I could make it. I installed the barreled action in a wood 40X stock to work up load data and work out any magazine feeding issues. While I was working on that, I looked for a McMillan Baker Special stock and finally found one to finish this project. I bedded the action and stock, then took the rifle to the range to check zeros on the sights and scope. I was surprised that I didn’t have to change anything on the sights. I thought changing the stock would cause sight changes. The thought went through my head, “Maybe the 40X stock isn’t all that bad”.
Here’s line-up of 6mm bullets. The Berger 95gr VLD is in the middle.
I took the new rifle to the first match of the year, a National Match Course match, and my off-hand score was 83, rapid sitting 95, rapid prone 95, and slow fire prone 197 — for total aggregate 470. This may not be my best work, but on match day the wind was blowing about 15 mph and the temp was around 40° F, with rain threatening. This was a reduced course of fire — we shot at 200 and 300 yards on reduced targets.
I used 70gr Berger bullets for this match, loaded in Remington brass with 25 grains of VihtaVuori N540 and Federal 205M primers. When I worked up loads for this rifle, N540 gave the best accuracy with the best extreme spread — 2,950 fps with an extreme spread of 20 fps on a 10-shot string. The load for 600 yards was with a 95gr Berger VLD bullet, with 23.0 grains of Reloder 15, Lapua cases, and the same Federal 205M primers. This load is 2,604 fps, with an extreme spread of 4 fps over a 10-shot string. I’ve shot this load at several 3×600 yard matches, and the accuracy has proven to be very good. At the last 3×600 match, my scores were as follows: 199-10x and 198-11X with scope, and 193-10X with iron sights. Best 600-yard score so far with iron sights was 198-12X.
6mm-223 Rem Rifle Specifications: 700 BDL action and floor plate, Bartlein 6mm 1:8″ twist, McMillan Baker Special stock in Desert Camo, Centra front and rear sights, Ken Farrell bases with stripper clip guide, Sinclair hand stop, and Jewell trigger. Gunsmith Neil Keller helped me with the metal work and instructed me on the action work and rebarreling.
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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 nearly 4.5 million 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 [with a standard short throat]. 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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If you want to use an AR-platform rifle in the varmint fields, consider getting a 20-caliber barrel chambered for the efficient, low-recoil 20 Practical cartridge. The 20 Practical is simply a .223 Remington necked down to 20 caliber. The parent .223 Rem cartridge of course works great in an AR, but the 20 Practical offers some notable advantages for high-volume varmint shooters. The 20 Practical delivers very high velocity with very low recoil while still providing outstanding accuracy. The 20 Practical is great option for folks who favor “fast and light” — smaller, lower-mass bullets traveling at very high velocities. This little cartridge can launch 40-grainers at over 3900 fps, and 32-grainers even faster. 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.)
Robert learned that the accuracy of the first 20 Practical AR15 was no fluke. After building six (6) more 20 Practical uppers, he tested them for accuracy and they all shot great. These uppers feature DPMS low-pro receivers with side-charging handles. They are fitted with PacNor 1:11″ twist, 3-groove stainless barrels.
Robert reports: “We have been making more 20 Practical AR15 uppers and I have to say I am astounded by the accuracy of these things. For shooting little tiny groups out of an AR15 with bullets going 3500+ fps, it’s hard to beat the 20 Practical. Today I test-fired six more uppers, all with 11-twist barrels. Three of the uppers had 24″ barrels, two had 20″ barrels, and one had an 18″ barrel (we call it ‘Stubby’).
In four of these uppers I shot re-sized Winchester brass using 25.3 grains of WC844 powder with Berger 40gr BTHP bullets loaded at 2.225″ OAL (about .015″ off the lands). WC844 is inexpensive military surplus powder that is nearly identical to H335. I tried three different primers and the choice did not seem to matter (CCI BR4, Rem 7 1/2s and Win Small Rifle — the old silver ones). All these four uppers shot great.”
Below is an animated GIF with targets from uppers #6, 10, and 11. All groups are mag-fed, 5-shot groups shot at 100 yards using a front rest and rear bag.
Targets Shot with Three Different 20 Practical AR Uppers
For more INFO visit www.6mmAR.com, or email: rcw3 [at] erols.com.
20 Practical Shooters Explain Why They Love this Little Cartridge
A current thread in our Shooters’ Forum focuses on favorite variants of the .223 Rem cartridge. The thread asks: “What is your favorite and most versatile round that you have made from a .223 Rem parent case?” Many cartridges were named, but the wildcat cartridge cited most often was the 20 Practical. Here are some comments by Forum members, who explain the appeal of this great little 20-caliber cartridge:
“The 20 Practical is just a hoot to shoot. Outstanding precision, minimal recoil, easy case forming and inexpensive to shoot. What’s not to like? It’s a great way to introduce kids to centerfire, too.” — JLT
“The 20 Practical for me. Never had as much fun shooting a rifle as I did with the 20 Practical. Also, [it is] the easiest wildcat to form. Just get cases, a couple of bushings to get the right neck tension, and you are shooting.” — NMKid
“Favorite .223 Rem Wildcat? The 20 Practical hands down for me. I have two of them built on Savage actions right now. One has a 20″ BHW barrel and the other has a 26″ Criterion. It is my go-to caliber for shooting up a Prairie Dog town and the ones I have are insanely accurate. Here are some typical 100- and 200-yard groups with my 20 Practicals.” — IA_Shooter
“My favorite was and is the 20 Practical. No fire-forming, no neck-turning, and with the increased BC of the 20 Cal bullets, it’s hard to wipe the smile off your face in a prairie dog town[.]” — Region Rat
“20 Practical and the [original] .223 Rem are my favorites. Accurate, cheap to shoot. The 20 Prac allows you to see your hits and it’s fast.” — Alguapo
“20 Tactical or 20 Practical. Both very easy to reload and/or form from .223 brass. And they are accurate, reach out on varmints at surprising ranges.” — Bill K
Smart Tips on Forming 20 Practical Cases
Varmint ace Warren B, aka “Fireball” in our Forum, explains how to form 20 Practical Cases. “Forming 20 Practical cases is very easy and no fire-forming is required. Start with any good quality .223 Rem brass. One can simply run the case into your bushing die with the appropriate bushing and call it done. I however like to make it a little more involved by doing the neck reduction in steps. I find that taking steps doesn’t overwork the brass as much as one step does. Also, if you resize the neck in too large of a step, sometimes, depending on the neck thickness, the neck will not be dimensionally what you would expect when finished. This is especially important towards the last step when one is getting close to the final required neck diameter.
For my cases the first thing I did was to run them into an old RCBS .223 Rem full length die with the decapping assembly removed. This will take care of any dented necks on the raw cases and bring the necks down to around 0.243″. Since all standard full-length dies oversize the necks way too much, starting with a .223 FL die actually reduces the neck diameter quite a bit–and obviates the need to buy an extra bushing for the first step. I then use my Redding Type-S die with two bushing sizes to get down to where I need to be. In other words, I start with the FL sizer, then move to a Type-S with a 0.233″ bushing and finish with a 0.228″ bushing. Notice how, as I get to the final step, I use progressively smaller increments in size between the reductions.” (Note: Depending on your brass your final bushing size may be different.)
20 Practical vs. 20 Tactical
Varminter Kevin Weaver, who shoots both the 20 Practical and 20 Tactical, states that: “Both the 20 Tactical and the 20 Practical are fine .20 caliber cartridges. However, my favorite would be the 20 Practical. The 20 Practical gives the SAME performance as the 20 Tactical without fire-forming, or having to buy expensive forming dies.
So with the 20 Practical you do less work, you shell out a lot less money, yet you give up nothing in performance. What’s not to like? To create 20 Practical cases, just buy a .223 Rem Redding Type “S” Bushing Die set with a .230 or .228 bushing and have fun with this great little cartridge.
The 20 Practical and the 20 Tactical are almost identical cartridges. There are only slight differences in case outside diameter, shoulder angle, and case body length. Neck length on the 20 Tactical is a bit longer, but there is still plenty of neck on the 20 Practical to grip the popular bullets, such as the 32gr V-Max.”
20 Practical and 20 Tactical Specifications:
Cartridge
Bolt face to shoulder
Shoulder O.D.
Shoulder Angle
Total length
20 Practical
1.5778″
.3553
23°
1.760″
20 Tactical
1.5232″
.360
30°
1.755″
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Intro: Ron Dague wanted a new gun that was similar to his trusty .223 Rem rifle, but which fired 6mm bullets. There is a superb choice of bullets in this caliber, and Ron found that the 95gr Berger VLD could be driven to a healthy 2604 FPS by the small .223 Rem case. This 6mm wildcat based on the common .223 Remington offers excellent accuracy and very low recoil — something very important in the cross-the-course discipline. In addition, Ron’s 95gr load with Alliant Reloder 15 delivered an ES of just 4 fps over ten shots. That exceptionally low ES helps achieve minimal vertical dispersion at 600 yards.
I have watched a change in thinking for NRA High Power across the course in match rifles and calibers. There are several [popular chamberings]: 6mm AR, 6.5 Grendel, 6XC, and 6.5 Creedmoor. I have seen these rifles perform and all have done very well.
When I started this project I was looking for a cartridge that shoots and feeds well from a magazine[.] I had shot the .223 Rem in my 722 Remington and knew it had fed well so I chose the .223 Remington necked up to 6mm.
The 6mm-223 gives me what I have in the standard .223 only with a better selection of bullets. I wanted a better 600-yard bullet with a higher BC than provided by the 80 and 82 grain bullets. I also wanted a 600-yard line bullet with a .500 or better B.C. for those shots that should be 10 ring or better but seem to find the 9 ring no matter how well I held and broke the shot.
Putting the 6mm-233 Project Together
My project started with ordering a 6mm barrel from Bartlein with a 1-8″ twist. I called Pacific Tool and ordered the 6mm-223 reamer. I found a used Remington 700 action at a local gun shop and already had a Remington 40X stock. I then started putting the gun together.
I already had a .223 Remington match rifle, and I wanted the 6mm-223 to be as close to the same as I could make it. I installed the barreled action in a wood 40X stock to work up load data and work out any magazine feeding issues. While I was working on that, I looked for a McMillan Baker Special stock and finally found one to finish this project. I bedded the action and stock, then took the rifle to the range to check zeros on the sights and scope. I was surprised that I didn’t have to change anything on the sights. I thought changing the stock would cause sight changes. The thought went through my head, “Maybe the 40X stock isn’t all that bad”.
Here’s line-up of 6mm bullets. The Berger 95gr VLD is in the middle.
I took the new rifle to the first match of the year, a National Match Course match, and my off-hand score was 83, rapid sitting 95, rapid prone 95, and slow fire prone 197 — for total aggregate 470. This may not be my best work, but on match day the wind was blowing about 15 mph and the temp was around 40° F, with rain threatening. This was a reduced course of fire — we shot at 200 and 300 yards on reduced targets.
I used 70gr Berger bullets for this match, loaded in Remington brass with 25 grains of VihtaVuori N540 and Federal 205M primers. When I worked up loads for this rifle, N540 gave the best accuracy with the best extreme spread — 2,950 fps with an extreme spread of 20 fps on a 10-shot string. The load for 600 yards was with a 95gr Berger VLD bullet, with 23.0 grains of Reloder 15, Lapua cases, and the same Federal 205M primers. This load is 2,604 fps, with an extreme spread of 4 fps over a 10-shot string. I’ve shot this load at several 3×600 yard matches, and the accuracy has proven to be very good. At the last 3×600 match, my scores were as follows: 199-10x and 198-11X with scope, and 193-10X with iron sights. Best 600-yard score so far with iron sights was 198-12X.
6mm-223 Rem Rifle Specifications: 700 BDL action and floor plate, Bartlein 6mm 1:8″ twist, McMillan Baker Special stock in Desert Camo, Centra front and rear sights, Ken Farrell bases with stripper clip guide, Sinclair hand stop, and Jewell trigger. Gunsmith Neil Keller helped me with the metal work and instructed me on the action work and rebarreling.
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.223 Rem for Long Range Palma, by John Whidden (5-Time Nat’l LR Champion)
We’ve seen quite an amount of interest in recent years in .223s for Long Range Palma shooting. Yes, the .223 Remington is a pretty light cartridge for long range use, but the specific rules of Palma shooting make it a choice worth considering.
Back in 2019, the Int’l Confederation of Fullbore Rifle Associations (ICFRA), the international governing body for Palma shooting, made a rule change allowing .223 Rem rifles to use bullets of less than 91 grains. Previously the rule allowed the use of bullets less than 81 grains in the .223 Rem, and we have long had the popular option of .308s shooting bullets less than 156 grains. These heavier bullets such as the 85.5gr Berger LR Hybrid and 90gr Berger VLD make the .223s quite competitive in the wind with the old standby .308 Winchester. The .223 does hold the obvious advantage of much lower recoil than the .308. [Editor: The reduced recoil is quite noticeable in the video below where John is shooting his .223 Rem rifle.]
John Whidden Shoots .223 Rem Palma Rifle with 90gr Berger VLDs
Watch video at 00:25 and you’ll see the recoil of Whidden’s .223 Rem Palma rifle is significantly less than a .308 Win Palma rig. John joked: “With the .223 Rem there is just a pop and a wiggle after the shot.”
.223 Rem Palma Rifle — Barnard Action, Tec-Hro Stock
The Barnard P action imported by Whidden Gunworks is the foundation for many winning Palma rifles. As soon as our USA shooters returned from the New Zealand Palma match in 2019 they were immediately requesting bolts to convert their actions to .223 Remington.
Given all of this interest in the .223 Rem, I decided to build one myself and see if all of these theories about wind performance held water. Starting with my Barnard P action, I worked with Tec-Hro in Germany to use one of their Fanatic stocks for the project. The Fanatic is a modern aluminum stock suitable for prone or Three Position use. The stock uses adapter blocks to work with a wide variety of rimfire actions such as Anschutz, Walther, and Feinwerkbau. As far as I know we were the first to test it out for centerfire use. After shooting the stock with my .308 Win barreled action installed to refine a few details and ensure the stock would stand up to recoil, I then mounted my .223 Rem barreled action and went to the range.
Prior to my range visit a decision was made concerning bullets and twist rate. After discussion with Mark Buettgen at Bartlein Barrels I ordered two barrels — a 1:7″-twist and also a 1:6.25″-twist. Mark was looking for some data using the Sierra 90gr MatchKing bullet and we expected that the faster twist rate might give the best success with that MatchKing bullet. When the barrels arrived they were chambered and installed on the rifle.
John uses a Warner rear adjustable sight with a Centra front sight.
Fast Twist-Rate Barrels for Long .223-Caliber Bullet
First up the 1:6.25″-twist barrel was installed and testing commenced. The barrel shot extremely well right out of the gate. All loads used Lapua brass and Vihtavuori N140 powder. I tested the Berger 85.5gr and 90gr bullets as well as Sierra 90gr and 95gr bullets. Testing with the 6.25-twist barrel went well with both of the Berger bullets looking especially good. Later the 1:7″-twist barrel was mounted and tested.
While both barrels were very accurate we decided that the 1:6.25″-twist barrel outshined the 1:7″-twist tube. Now we all know that some barrels are just a little more accurate than others. With such a small sample of data here (just two barrels) I’m not saying that a 1:6.25″-twist is decidedly better. In fact we have a number of customers shooting 7-twist barrels who are shooting them very well. With this particular rifle however, the 6.25-twist seems to be the more accurate of the two.
.223 Rem Load Development for Palma Competition
The load I settled on is Lapua brass, Vihtavuori N140 powder, and Berger 90 grain VLDs which I moly-coat. I soft-seat the bullets into the lands with only .001″ neck tension or a little less.
Why the Berger 90gr VLD? The secret sauce is that the 90gr VLD is much superior in the wind after we point it up with the Whidden Pointing Die. The 85.5gr Hybrid bullet comes from Berger with this treatment already done while the 90gr VLD does not. When the 90-grainer is pointed up, the wind drift is a few percent better than the 85.5, given the velocities that I feel comfortable achieving with the rifle.
I settled on 2840 fps for the 90gr VLD and 2880 fps for the 85.5gr Hybrid from a 32″ barrel. When pointed up, the 90-grainer shoots flatter to 1000 yards by 1 MOA which indicates a G7 BC of .289 in my combination. Wind Drift in a 10 mph direct crosswind at 1000 yards is 70.8″ with this 90gr combination compared to 76.8″ for the 85.5gr load.
Testing in Competition — at Camp Perry
This past August 2021 at the CMP Long Range National Championships at Camp Perry I finally had the chance to shoot the rifle on a big stage. Winds that day were from almost directly 12:00 to about 1:30 switching headwinds. Velocity was around 8-10 mph meaning not the easiest or the hardest of conditions. I managed a third place finish in the Palma match. That proves the .223 Rem is definitely competitive in elite Palma events.
.223 Rem Performance in the Wind
My sense of the .223 Rem’s wind performance was that it was in line with the performance I’d expect from my .308 Win Palma gun. Of course the lack of recoil made the .223 Rem much easier to shoot well.
How to Order a Rifle Like This Whidden Gunworks can build a rifle like this for Palma competitors who want to move to .223 Rem. John tells us: “We’ve built a number of these combinations of the Barnard P action, Tec-Hro Fanatic stock, and Bartlein barrel. They all shoot incredibly well and the ergonomics are top notch. One of the good points is that the current price of $3875.00 (without sights) makes it a bargain for a top-tier Palma rifle.”
About John Whidden
5-Time National Long Range Champion
John Whidden is founder and owner of Whidden Gunworks and a lifelong competitive shooter. Major shooting accomplishments include being a 5-Time U.S. National Long Range Champion, winner of the Australia National Queen’s Prize, and member of three USA Palma Teams. John is currently active in Long Range Highpower, 300 Meter Prone, and Smallbore prone events. John tells us that one secret of his success is having top equipment: “The mental component of Long Range competitive shooting is always challenging but having tremendous confidence in the accuracy of your equipment is a huge benefit. There’s nothing to start your Palma match off well like knowing that you are shooting the most accurate Palma rifle you’ve ever owned.”
Whidden Gunworks stands ready to help with your shooting and reloading needs. Whidden Gunworks specializes in custom bolt action rifles, reloading dies, other reloading tools, and reloading components. Well known for match-grade custom rifles and high-quality reloading dies, Whidden Gunworks’ growing lineup includes components from Berger, Lapua, Vihtavuori, and SK rimfire ammunition. Learn more by visiting www.WhiddenGunworks.com.
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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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Intro: Ron Dague wanted a new gun that was similar to his trusty .223 Rem rifle, but which fired 6mm bullets. There is a superb choice of bullets in this caliber, and Ron found that the 95gr Berger VLD could be driven to a healthy 2,604 fps by the small .223 Rem case. This 6mm wildcat based on the common .223 Rem offers excellent accuracy and very low recoil — something very important in the cross-the-course discipline. In addition, Ron’s 95gr load with Reloder 15 delivered an ES of just 4 fps over ten shots. That exceptionally low ES helps achieve minimal vertical dispersion at 600 yards.
I already had a .223 Remington match rifle, and I wanted the 6mm-223 to be as close to the same as I could make it. I installed the barreled action in a wood 40X stock to work up load data and work out any magazine feeding issues. While I was working on that, I looked for a McMillan Baker Special stock and finally found one to finish this project. I bedded the action and stock, then took the rifle to the range to check zeros on the sights and scope. I was surprised that I didn’t have to change anything on the sights. I thought changing the stock would cause sight changes. The thought went through my head, “Maybe the 40X stock isn’t all that bad”.
Here’s line-up of 6mm bullets. The Berger 95gr VLD is in the middle.
I took the new rifle to the first match of the year, a National Match Course match, and my off-hand score was 83, rapid sitting 95, rapid prone 95, and slow fire prone 197 — for total aggregate 470. This may not be my best work, but on match day the wind was blowing about 15 mph and the temp was around 40° F, with rain threatening. This was a reduced course of fire — we shot at 200 and 300 yards on reduced targets.
I used 70gr Berger bullets for this match, loaded in Remington brass with 25 grains of VihtaVuori N540 and Federal 205M primers. When I worked up loads for this rifle, N540 gave the best accuracy with the best extreme spread — 2,950 fps with an extreme spread of 20 fps on a 10-shot string. The load for 600 yards was with a 95gr Berger VLD bullet, with 23.0 grains of Reloder 15, Lapua cases, and the same Federal 205M primers. This load is 2,604 fps, with an extreme spread of 4 fps over a 10-shot string. I’ve shot this load at several 3×600 yard matches, and the accuracy has proven to be very good. At the last 3×600 match, my scores were as follows: 199-10x and 198-11X with scope, and 193-10X with iron sights. Best 600-yard score so far with iron sights was 198-12X.
6mm-223 Rem Rifle Specifications: 700 BDL action and floor plate, Bartlein 6mm 1:8″ twist, McMillan Baker Special stock in Desert Camo, Centra front and rear sights, Ken Farrell bases with stripper clip guide, Sinclair hand stop, and Jewell trigger. Gunsmith Neil Keller helped me with the metal work and instructed me on the action work and re-barreling.
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Here’s an entertaining video from Fog Ammunition. 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):
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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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If you own an AR, you’ve probably heard of the hot, new .224 Valkyrie cartridge. Basically a 6.8 SPC necked down to .22, 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. With Sierra’s remarkable new 95-grain MatchKing, this gives the little Valkyrie long-range performance that can rival some much larger cartridge types. Sierra Bullets states: “The [Valkyrie] case length is shorter than the 223 Remington affording the use of heavier match-grade bullets with very long ogives and high ballistic coefficients. This offers … super-sonic velocities at ranges greater than the .223 Remington and the 6.5 Grendel can achieve at magazine length”.
If you’re considering a .224 Valkyrie, you’re in luck — Sierra Bullets has just released comprehensive LOAD DATA for this new cartridge. Sierra has published loads for a broad range of bullet weights from 52 grains all the way up to 95 grains. Loads for 20 bullet types and 22 powders* are listed.
Shown below is Sierra’s load data for bullet weights from 77 grains to 90 grains. Values in green indicate MAXIMUM loads — use CAUTION. NOTE: This is only a partial sample, less than a third of the data Sierra has published. Download Sierra’s Full 4-page PDF to view all the data, including load information for Sierra’s new 95gr .224-caliber MatchKing with claimed 0.600 G1 BC.
The new .224 Valkyrie was introduced late last year as a Hot Rod cartridge that will work in AR15s. Designed to rival the .22 Nosler while still running well in ARs, the new .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. Check out this chart from Federal showing comparative recoil levels:
* All the following powders were tested, but not all for each bullet weight: Accurate 2520, Accurate XMR 2495, Accurate 4064, Hodgdon AR Comp, Hodgdon Benchmark, Hodgdon CFE 223, Hodgdon H335, Hodgdon H380, Hodgdon H4895, Hodgdon Varget, IMR 4064, IMR 4166, IMR 8208 XBR, Power Pro 2000 MR, Power Pro Varmint, Ramshot Big Game, Ramshot TAC, Reloder 10X, Reloder 15, Reloder 17, Vihtavuori N540, Winchester 760.
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Here is a great deal on a great little rifle. Right now at Cabela’s you can get the Howa 1500 Mini-Action in .223 Rem for just $314.99 with Coupon Code 16STALKUP. The rifle (with black synthetic stock) is already on sale, marked down to $349.99. That discount code gives you another 10% off. That’s a bargain — other vendors are charging $515.00 or more for this rifle. We actually “walked through” the online ordering process ourselves to confirm that the discount code works (see below). Note, you order online, but the rifles must be picked up in a Cabela’s store.
The Howa 1500 Mini Action is nearly an inch shorter than a Rem 700 short action, making for a nice, compact carry-around varminter (OAL length is just 41.5″). Your Editor checked out the Howa Mini Action Rifle at SHOT Show. The bolt opens and closes VERY smoothly (way better than most mass-produced bolt guns). The two-stage HACT trigger is excellent — it’s plenty light, with a crisp release and no annoying spring-loaded blade in the middle. I like it MUCH better than standard Remington, Ruger, or Savage triggers.
The standard Howa Mini Action rifle weighs 6 pounds without scope. This particular model comes with a 22″ barrel, black synthetic stock, and 10-round detachable box magazine. The Howa Mini on sale at Cabelas.com is a .223 Remington, but other chamberings are available at a higher price if you shop around. Howa offers Mini Action rifles in .204 Ruger, .222 Rem, .223 Rem, 6.5 Grendel, and 7.62x39mm.
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Based on the questions we get on a daily basis on our 800 (Customer Support) line, twist is one of the most misunderstood subjects in the gun field. So let’s look deeper into this mystery and get a better understanding of what twist really means.
When you see the term 1:14″ (1-14) or 1:9″ twist, just exactly what does this mean? A rifle having a 1:14″ twist means the bullet will rotate one complete revolution every fourteen inches of the barrel. Naturally a 1:9″ turns one time every nine inches that it travels down the barrel. Now, here’s something that some people have trouble with. I’ve had calls from shooters thinking that a 1:14″ twist was faster than a 1:9″ because the number was higher with the 1:14″. The easiest way to remember this is the higher the number, the slower the twist rate is.
Now, the biggest misconception is that if a shooter has a .223 with a 1:8″ twist, his rifle won’t stabilize a 55gr bullet or anything lighter. So let’s look at what is required. The longer a bullet is for its diameter, the faster the twist has to be to stabilize it. In the case of the .223 with a 1:8″ twist, this was designed to stabilize 80gr bullets in this diameter. In truth the opposite is true. A 1:8″ will spin a 55gr faster than what is required in order to stabilize that length of bullet. If you have a bullet with good concentricity in its jacket, over-spinning it will not [normally] hurt its accuracy potential. [Editor’s Note: In addition, the faster twist rate will not, normally, decrease velocity significantly. That’s been confirmed by testing done by Bryan Litz’s Applied Ballistics Labs. There may be some minor speed loss.]
Many barrel-makers mark the twist rate and bore dimensions on their barrel blanks.
Think of it like tires on your truck. If you have a new set of tires put on your truck, and they balance them proper at the tire shop, you can drive down a street in town at 35 MPH and they spin perfect. You can get out on the highway and drive 65 MPH and they still spin perfect. A bullet acts the same way.
Once I loaded some 35gr HP bullets in a 22-250 Ackley with a 1:8″ twist. After putting three shots down range, the average velocity was 4584 FPS with an RPM level of 412,560. The group measured .750″ at 100 yards. This is a clear example that it is hard to over-stabilize a good bullet.
Twist-rate illustration by Erik Dahlberg courtesy FireArmsID.com. Krieger barrel photo courtesy GS Arizona.
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By Ron Dague, Sinclair Reloading Tech
Putting the 6mm-233 Project Together
20 Practical Ultimate Varminter
Varminter Kevin Weaver, who shoots both the 20 Practical and 20 Tactical, states that: “Both the 20 Tactical and the 20 Practical are fine .20 caliber cartridges. However, my favorite would be the 20 Practical. The 20 Practical gives the SAME performance as the 20 Tactical without fire-forming, or having to buy expensive forming dies.
Putting the 6mm-233 Project Together
Testing in Competition — at Camp Perry
About John Whidden
