Dented shoulder brass from AR 10?

[rmiked]

Shot my Seekins SP10 (6.5 CM) today first time. Shot great IMO. The Hornady 140 ELDM and Hornady 129 American Whitetail both shot 3 shot groups of 7/8”. The Winchester 129 PP was 1.5” group. The rifle loaded, ejected, locked back and was properly gassed with cartridges flying in the 3-5 o’clock direction. I noticed all the brass is somewhat dented below the base of neck on shoulder. Being new to ARs I had heard about this. The ejected brass colliding with shell deflector causes this. I assume it’s normal for a gas gun? If you reload, pushing a case into a sizer die will confirm the exterior case dimensions. I don’t see the dent going away except due to pressure on next firing, then hitting the shell deflector again on the way out. Just size them and reload anyway?

 

[bfoosh006]

Attach a adhesive backed, fuzzy side of velcro tape to your brass deflector.

 

[rmiked]

Thanks! Great idea

 

[rmiked]

BTW: I shot a 3 shot group of SIG Elite Hunter , 130 grain tipped. Group was 9/16”. I measured the cartridges. The Hornady 140 ELDM is 2.810” OACL. The SIG 130 is 2.825 and will fit in the magazine , feed fine. But I don’t think any longer cartridges will fit a Magpul Pmag. I only shot 17 rounds today, first time out. Just sighting in rifle and trying 4 different loads (factory). I would hunt with the Hornady 140 ELDM,Hornady American Whitetail 129 or the SIG 130 Elite Hunter. All under 1” groups at 100 yds for 3 shots. Never fired an AR before today. I like this rifle. Low recoil and accurate. The Nightforce NXS 2.5-20 is sweet also.

 

[bfoosh006]

https://magpul.com/pmag25m118lr-srgenm3window-7-62x51.html?mp_global_color=118

And the 10rd mag says the same thing...

https://magpul.com/pmag-10-lr-sr-gen-m3.html?mp_global_color=118

FWIW... the 25rd and 10rd, Magpul M118 mags say they will accept up to "Optimized for use with 7.62x51 M118LR or other .308 Winchester match ammunition with a max OAL of 2.830"

And I forgot to mention, sometimes cases can get dented from the barrels bolt lugs by the ejection port upon ejection.

 

[bfoosh006]

Oops, and Padom has reported, KAC and Larue LR/SR25 mags allow 2.871.

Expensive mags, but... "Built like a Tank"

 

[samnev]

Attach a adhesive backed, fuzzy side of velcro tape to your brass deflector.

Been doing that for years and it works great!!

 

[db2000]

And if you just want to spend money these work great.