300 Win Mag brass issues

[DenverGP]

Not my gun, but I'm sending an email to the owner of the gun.. I don't know if these rounds were factory or reloads. They were all hornady headstamps.

This was brass I picked up at the range, being fired from a 300 Win Mag AR-10 (at least AR-10 style rifle).

About half of the brass had primers knocked part way or all the way out. Several showed flattened primers.

And many had some kind of damage on the back of the rim.. the damage wasn't on the side or where the extractor grabs, so I'm guessing the damage was caused by gasses leaking past the primer.

[Colorado Osprey]

Not uncommon in a high pressure gas operated gun when the chamber unlocks before the pressure is released. This is also seen in the WSSM line of AR's. Also, the brass expansion is also so large that a lot of the time you can not even insert the same used brass back in the gun it was just shot from.
Not sure what your plans were for the brass, but before you invest too much time in them, you might run one through a full size sizing die and see if the belt has enlarged enough to prevent you from chambering it into another gun if you planned on reloading it.

[C Ward]

Brass is garbage, case head is swollen and the primer pocket expanded.

[Slapps74]

Brass is garbage, case head is swollen and the primer pocket expanded.

X2

[DenverGP]

Not worried about re-using the brass, mostly just collected for coolness... was mainly concerned if the condition of the brass suggested the ammo was loaded too hot, or possibly issue with the rifle. Based on Osprey's post, sounds like it's not unusual for this type of ammo in a gas operated gun. Guess that makes sense.

[C Ward]

Yes too hot for that rifle , has every one of the classic pressure signs .
Flat primers
Smoked primers
Blown primers
Ejector marks
Bent rim

[Zombie Steve]

I don't know about AR platforms shooting .300 mag. Makes sense what Osprey is saying... but my first thought seeing the primers backed out and gas leakage was that the load is too hot and the shoulders were pushed too far creating a headspace issue.

???

[Jamnanc]

Isn't a possible fix to install an adjustable gas block and limit how quickly the action starts to cycle?

[Zombie Steve]

I can only imagine with the slow powders that it takes to run the .300 win mag that the port pressure is downright abusive.