Question re flat spot on brass from an AR 10

Status
Not open for further replies.

TomJ

Contributing Member
Joined
Jul 3, 2014
Messages
2,942
Location
SE Wisconsin
A friend of mine has an AR 10 that's causing a flat spot on his spent brass. He asked if I knew what could cause this, but I don't know that much about the AR platform. Has anyone experienced this or have any suggestions?


IMG_6114.jpg
 
That’s the case smacking the shell deflector. It happens with some semiautos. If you don’t reload, nothing to worry about. If you reload, you just need to clean, lube and resize it.


This video clearly shows what’s happening, however this is an AR15. Same thing happens on an AR10

 
Last edited:
If it is a flat dent below the shoulder, it’s happening as brass deflects off of the deflector on the outside of the receiver. Tuning down gas and sticking some “loop side” 3M velcro on the deflector will stop that.

If it’s a flat side of the case neck/mouth, it’s happening as the case is extracted, because the ejector presses the case against the port side inside of the extension. Just live with it. You CAN reduce it by clipping coils from your ejector spring, but it’s not a good thing to make that weaker…
 
Just resize it IMHO. I should post up some pics of the 54R brass one of my automatics destroys....yup destroy is the correct word. You can turn down an SVT, but off the top of my head you can't on a PSL.

If I remember I will post up some of that brass.
 
Its a very common thing and nothing to worry about, even if you reload.

If you think that's bad, you should see what an HK91 without a port buffer does to brass. :)
 
Its a very common thing and nothing to worry about, even if you reload.

If you think that's bad, you should see what an HK91 without a port buffer does to brass. :)

Yeah, my HK really chews it up! :fire:

I keep a polished center punch on my loading bench for rounding out bent case mouths although the expander ball takes care of minor dings like the one pictured just fine.
 
Status
Not open for further replies.
Back
Top