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What’s going on here?

It's over pressured! I had a guy blowing primers left and right with his Omen 300 WM AR. The Super performance is not made for an AR platform because of the chamber pressures. They do fine in a bolt action rifle, they can handle the higher pressure.

Switch ammo and problem solved. You can adjust the gas block, but are still over pressured for the AR
 
Friend just bought a Ruger SFAR 308. 20" barrel. Super light. He did some break in shoot/clean yesterday. Sighted it in today with factory Hornady Superformance 150 grain bullets. Here is a picture of the case head. Speeds were right around 2850. What causes this?
View attachment 555876
Jeepers that looks bad!

What I can't figure is the primer isn't pierced, pancaked, or cratered, and the velocity listed isn't anything eyebrow raising, right where it should be for full performance.

And no issues with extraction and ejection?
 
It's over pressured! I had a guy blowing primers left and right with his Omen 300 WM AR. The Super performance is not made for an AR platform because of the chamber pressures. They do fine in a bolt action rifle, they can handle the higher pressure.

Switch ammo and problem solved. You can adjust the gas block, but are still over pressured for the AR

I'll pass it on.
Thanks!
 
Jeepers that looks bad!

What I can't figure is the primer isn't pierced, pancaked, or cratered, and the velocity listed isn't anything eyebrow raising, right where it should be for full performance.

And no issues with extraction and ejection?

Everything looks good except what doesn't. Ejected fine.

I think gas block will get checked. Then different ammo will be best route.
 
It's over pressured! I had a guy blowing primers left and right with his Omen 300 WM AR. The Super performance is not made for an AR platform because of the chamber pressures. They do fine in a bolt action rifle, they can handle the higher pressure.

Switch ammo and problem solved. You can adjust the gas block, but are still over pressured for the AR
How is an AR chamber different pressure rating than a bolt chamber of the same caliber?
 
How is an AR chamber different pressure rating than a bolt chamber of the same caliber?
It isn't. Moreover regardless of what kind of action it's fired in if the pressure is so high as to cause all these signs there should be other signs! But the OP reports no issues with chambering OR extraction and ejection, and that primer looks perfectly acceptable, no pancaking or cratering or anything.

No there's definitely something more going on here. Also hornady superformance ammo doesn't come with any "for bolt guns only" disclaimer and if that truly was the reason this happened they'd have been getting sued left right and center you'd think for NOT issuing that warning.
 
How is an AR chamber different pressure rating than a bolt chamber of the same caliber?
You're correct, I should expound rather than rush a post, 🤦

There's a dwell time issue causing an overage in pressure because of the gas system. Pressure is fine in either, the bolt gun can handle more and has different pressure signs, like hard to lift bolt, etc. Gas guns blow primers, or have major ejector swipes.

Also, in general the bolt gun can handle higher pressure without some major damage because of a gas system, if what I'm saying is making sense....
 
I've been shooting a six arc for a little while now. Hornady actually has different published data for six arc in a semi auto gun versus a bolt gun.
Interesting to learn.
Is it just ballistic data or is it specific to chamber pressure?
 
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