(Do NOT Do This) Alpha Munitions 6mm ARC High Pressure Test

Alpha Munitions’ OCD technology has made it possible for us to run some absolutely extreme experiments, none of which you should try yourself. This time, we pushed Alpha Munitions 6mm ARC brass to the limit of the gun, blowing up an AR-15 in the process! Watch the full video and read on for more specifics.

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High Pressure Research

For the sake of research, we’ve pushed 308 Winchester to 300 Win Mag levels with Alpha Brass as well as run 6GT to the max.

6GT High Pressure Rig Mounted on the Arrow Products Rock Vise

These videos have all confirmed the strength of Alpha brass.

Once again, do NOT attempt anything shown in these videos.

I’d also like to note that I’ve also observed great accuracy with ammunition loaded in Alpha Munitions cases. During load development for my 6 Dasher, I fired a five-shot group at 100 yards measuring 0.09”!

6mm ARC Bolt-Gun Testing

6mm ARC has exploded in popularity in both the bolt-gun and AR realms and I wanted to push the performance of the caliber as far as it could go. After conferring with Alpha Munitions, I selected IMR 8208 XBR for the high-performance cartridge, pairing it with Berger 6mm 109-Grain Long Range Hybrid Target Bullets in virgin Alpha Munitions casings.

I started off my test with a 6mm ARC bolt-action I built on the channel featuring a BAT TR action, Bartlein 24” 1:7.5 barrel, TriggerTech Diamond 2-stage trigger, and Leupold scope.

We used this same rifle in the ELR stage of the Rock Chuck Olympics, but have since added a suppressor as we are shooting from inside a building to block some of the winter air.

I loaded up eight different charge weights from 24 grains to 31 grains on the Area 419 ZERO press.

31 grains was the limit of IMR 8208 XBR for 6mm ARC. No more powder would fit in the case and I had already seated the bullet out as far as I was comfortable.

I fired the bolt-action off a tripod and recorded velocity data with the Athlon RangeCraft Velocity PRO chronograph.

Alpha 6 ARC Bolt Gun High Pressure Results

Each additional grain of powder added approximately 100 fps to the velocity.

By shot six with 29 grains of powder, I began to see subtle pressure signs on the case rim, but zero bolt lift. 30 grains of powder yielded a velocity over 3,000 fps. For reference, Hornady factory 6mm ARC ammunition averages a muzzle velocity of 2,750 fps and Hornady 6mm Creedmoor ammunition averages 2,960 fps. (Once again, do NOT do this at home.)

Hornady 6mm ARC 108-Grain ELD-M Factory Ammo Velocity Table

Hornady 6mm Creedmoor 108-Grain ELD-M Factory Ammo Velocity Table

I was a bit nervous pulling the trigger on the final cartridge loaded with 31 grains of IMR 8208 XBR. It went off safely, but the case showed considerable ejector swipe.

6mm ARC Pressure Testing, Shots 1-8 Labeled

The primer remained intact and unpierced at 3,092 fps.

This is 342 fps over factory 6mm ARC ammunition and 132 fps over factory 6mm Creedmoor ammunition with 108-Grain ELD-M projectiles.

I also took the time to measure the base diameter and extraction groove diameter of each case after firing.

Base diameter growth of 0.01” or more is indicative of high pressure. Impressively, total base diameter growth in our test was 0.00485”.

The extraction groove diameter grew by a total of 0.0055”. (This measurement is more prone to measurement error due to limitations of measuring equipment.)

Do NOT Do This at Home – Blowing up an AR

Having maxed out the amount of IMR 8208 XBR I could use and still not having found the limit of Alpha’s cases, I decided to transition to a 6mm ARC AR-15. (AR-15’s are not as strong as bolt-actions.) I repeated the experiment with new cases, loading charges from 23 grains to 31 grains of IMR 8208 XBR. In the interest of safety, I secured the rifle in a vise outside, monitored by a high-speed camera.

I attached a long string to the trigger and only pulled it when I was safely inside behind a door.

Just as I had observed during my bolt-action testing, adding one grain of powder yielded approximately a 100 fps increase in velocity. By the 29-grain-mark, the brass displayed intense pressure signs, much more than with the same charge weight in the bolt-action. With 0.008” extra clearance in the AR and less support for the case rim, the case head is able to swell. I continued, 30 and 31 grains yielding approximately equal velocities of 2820 and 2822 fps. These cases had to be manually pulled out of the bolt.

It’s important to note that the differences in velocity between the same loads fired in the bolt-action and AR are due partly to barrel length and to the AR’s gas system.

In short, we were unable to destroy a case of 6mm ARC Alpha Munitions brass with an appropriate powder. Determined to see what it would take, I decided to try an inappropriate powder. This is something you should NEVER do.

I filled a brand-new Alpha Munitions case with Hodgdon Universal Clays — a fast pistol and shotgun powder, and weighed the charge. I did not do any load work-up for this part which is NOT advisable.

21.8 grains of Clays recorded a velocity of 4,728 fps and destroyed the gun in the process.

Alpha 6 ARC AR-15 High Pressure Results Table

The sound from behind the door was completely different from previous shots.

When we ventured out to investigate, we discovered that the bolt carrier had blown up and the magazine and floor plate had blown out.

It was quite impressive to watch the destruction in slow-motion!

Conclusion

I have previously observed the quality of Alpha Brass, but was still shocked we were unable to destroy a piece of their 6mm ARC brass with an appropriate powder across two different platforms.