What’s going on here?

[dustbag]

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?

 

[FireFlyFishing]

Really hot load? Try some different ammo?

 

[dustbag]

I thought maybe something with the gas. I don't know much about ARs but yeah he won't be shooting any more of that ammo til it gets figured out.

 

[Koda_]

It could be he's overgassed. I'm curious about the mark opposite the extractor impressions. Is the case rim bent outward in that area? He might need to adjust the Ruger gas block.

 

[dustbag]

I don't know if rim is bent. I'll have him check the gas. Thanks.

 

[Mike6158]

I've never seen an AR base look like that and I've shot some hot loads. The primer doesn't look flat. The primer isn't cratered. I couldn't see extractor marks on the rim. When mine are over-gassed they bend the crap out of the case mouth. What does the ejection pattern look like. Ie is the brass landing forward of ejection, 3 o'clock (90 degrees), or behind ejection. I hope you find out what caused it. I'm curious.

 

[dustbag]

2-3 o'clock

 

[Mike6158]

2-3 o'clock

That's perfect. WTH??

 

[FireFlyFishing]

Suppressed? I agree on over gassed.

 

[dustbag]

No suppressor came with side port brake.

 

[Koda_]

I don't know if rim is bent. I'll have him check the gas. Thanks.

note: it doesn't have to be obviously bent, its just that in overgassed situations the extractor will often bend the rim trying to extract the case before pressure has dropped in the chamber. Ive heard this can also cause ejector swipes, falsely indicating pressure.
If the rifle is new it could be he needs to set up the adjustable gas block. I would have him check his owners manual if thats needed.

 

[dustbag]

Just gave him this info. He's gonna look at manual and check gas block. If he figures it's over his head he's gonna take to shop where he got it and have them look at it. Thanks for all the info.

 

[Berrnard]

was the round hard to chamber?
it kinda looks like the round was in so tight that the bolt head scaped the rim as it opened up to eject
round could be too long and the bullet is being pushed into the grooves

 

[338 dude]

Dual ejectors plus a hot load