What’s going on here?

[quigley257]

From Hornady...

Superformance in Gas Operated Firearms - Hornady Manufacturing, Inc

Background Superformance ammunition was developed in the Hornady ballistics lab utilizing state of the art test equipment in accordance with SAAMI (Sporting Arms and Ammunition Manufacturers Institute) guidelines for pressure, velocity and accuracy ut...

www.hornady.com

 

[dustbag]

From Hornady...

Superformance in Gas Operated Firearms - Hornady Manufacturing, Inc

Background Superformance ammunition was developed in the Hornady ballistics lab utilizing state of the art test equipment in accordance with SAAMI (Sporting Arms and Ammunition Manufacturers Institute) guidelines for pressure, velocity and accuracy ut...

www.hornady.com

Thanks for posting this. I will forward it along.

Dustin

 

[338 dude]

Interesting to learn.
Is it just ballistic data or is it specific to chamber pressure?

 

[dustbag]

Update

Gas was at 3 setting which is wide open. He set it to 2 and shot the 150 grain Superformance. Same result. Set gas to 1 and shot Superformance load. Case head was fine but bolt didn't cycle far enough to eject.

Set gas back to 2 and shot factory Winchester 150 load and everything went as it should.

We learned no Superformance factory loads in that gun and gas at 2 is the sweet spot.

Thanks everyone for your input. Problem solved in less than 24 hours.

Dustin

 

[Koda_]

View attachment 556156
View attachment 556157

Again, interesting to learn. It sounds like the 6ARC is specific to chamber pressure. This wouldn't be the first cartridge built specific to the AR15 platform but I wonder why Hornady bothered with increasing the chamber pressure in bolt guns?

Seems like that would add some potentially dangerous confusion similar to firing a 357mag in a 38spl revolver.

 

[ncwg2boatguy]

Interesting to learn.
Is it just ballistic data or is it specific to chamber pressure?

Hornady has it in reloading data manual

 

[ncwg2boatguy]

 

[ncwg2boatguy]

In Hornady reloading manual gas gun pressure is 52000 PSI bolt gun is 62,000 PSI

 

[HNDLDR]

I agree with all that have mentioned over gassing. The Hornady article explained this well. The AR10 style guns with smaller bores (243s my 7mm-08) tend to amplify this issue, especially with slower powders. The only thing I might add is if the adjustable gas block adjustment is too coarse maybe try adjusting the buffer weight a little heavier. I bought some tungsten weights to change out with the steel ones in the buffer. As I understand it this helps slow the opening of the action like the adjustable gas block does.

 

[T3ninja]

Update

Gas was at 3 setting which is wide open. He set it to 2 and shot the 150 grain Superformance. Same result. Set gas to 1 and shot Superformance load. Case head was fine but bolt didn't cycle far enough to eject.

Set gas back to 2 and shot factory Winchester 150 load and everything went as it should.

We learned no Superformance factory loads in that gun and gas at 2 is the sweet spot.

Thanks everyone for your input. Problem solved in less than 24 hours.

Dustin

Hey, the gas system might have to coarse of adjustment , BUT what I'm seeing is not necessarily a hot load or over gassing. It looks to me like more of a timing issue. The bolt is trying to unlock and extract before peak pressure has dropped off enough for the casing to shrink and let go of chamber walls. That's why you are seeing the ejectors twisting on the case IMO. I would try finding the heaviest weight buffer you could get your hands on. Put that in and see if it changes.

 

[quigley257]

Again, interesting to learn. It sounds like the 6ARC is specific to chamber pressure. This wouldn't be the first cartridge built specific to the AR15 platform but I wonder why Hornady bothered with increasing the chamber pressure in bolt guns?

Seems like that would add some potentially dangerous confusion similar to firing a 357mag in a 38spl revolver.

Bolt guns can handle the 60K+ pressures that would beat up a gas gun. I have built both 223 Rem and 224 Valkyrie bolt guns that are throated long enough for the high BC bullets(I shoot 88ELDMs in both) to be seated with the boat tail heel right at the junction of the case neck. Bolt guns aren't hindered by the same magazine length restrictions(2.260") that gas guns are. A long throated bolt gun allows longer OAL, which increases powder capacity and velocity potential as well as running higher chamber pressures than you will see listed for standard 223 and 224 data. The 6ARC is more of a crossover cartridge so Hornady made data available for gas and bolt guns.

 

[MOA or bust]

error

 

[HNDLDR]

The AR platforms have steel locking lugs locking directly into a steel barrel and can handle the same pressures as a bolt gun. They do however have to be timed properly so the bolt is not opening too soon. If not timed correctly this is what beats up brass and can damage rifles, especially aluminum receivers.

 

[HNDLDR]

And yes changes in ammunition like bullets taking up more space in the case. (Reduction of case capacity) will increase pressure to unsafe levels just the same as it will in a bolt gun.