Case mouth denting in gas gun

[Tom3006]

I just noticed the once-fired brass from my AR10 is consistently being dented at the case mouths. The rifle is a Live Free Armory AR10 in .308 Win. The ammo is Black Hills Gold .308 Win Match with 168 gr Hornady A-Max. I didn't experience any failures to feed, chamber or eject. The rifle shoots really well actually (just under 1 MOA). I probably have less than 80 rounds through it. Thanks for your comments.

 

[Pres100]

That will iron out fine in your sizing die and be fine. Typical for a lot of gas guns

 

[olddav]

Are you asking why the case mouth is dented?

 

[jerseyjoe]

They are being dented by the shell deflector on the upper.

I use an old tapered punch that I polished to shove in the dented case mouths to

open them up before I size them.

 

[Rsadams]

Do you know what size gas ports in it... If it's an over gas issue a heavier spring and buffer will cure it..

Sprinco springs is what I use in my M4s. They last very well..

 

[T-shooter]

Probably hitting the deflector. Try a 1/8" pad of black silicone on the front side. Easy to remove if that's not the problem. My AR15 beat the brass up, sometimes making it unusable with large dents in the shoulder with certain loads.

 

[seymour fish]

Do you know what size gas ports in it... If it's an over gas issue a heavier spring and buffer will cure it..

Sprinco springs is what I use in my M4s. They last very well..

Sprain on. Excellent products and great people. Concurrent with your assessment here

 

[seymour fish]

Sprain on. Excellent products and great people. Concurrent with your assessment here

Sprinco !

 

[Richard Coody]

Probably hitting the deflector. Try a 1/8" pad of black silicone on the front side. Easy to remove if that's not the problem. My AR15 beat the brass up, sometimes making it unusable with large dents in the shoulder with certain loads.

The cure

ARs are hard on brass

 

[people]

Very much a common issue with certain loads. padding the shell deflector will help. Adding weight to the carrier will help also. The extra mass might affect how it shoots.

 

[Tom3006]

I see. I don't shoot gas guns often so I'm not used to seeing this. Thanks for your replies!

 

[jdj71]

a piece of velcro (fuzzy side )on the shell deflector will help with that and yes gas guns are hard on brass

 

[Brian Moeller]

Or adjustable gas block will work

 

[Rsadams]

Sprinco !

I had no idea they were right down the road from me.. Their chrome silica spring will supposedly last the life of the barrel... Altho normal stainless springs are cheap and don't rust I don't take mine to the beach much...lol.. I just decided to try a sprinco and stayed with them..

The heavier buffer and spring are not expensive... And can be changed by anyone.. No gunsmith needed...there's no reason to let a gun beat on itself... Your looking for about a 4:00 o'clock ejection...

 

[gunsandgunsmithing]

That's a bit excessive. I'd put an adjustable gas block on it and tune it a bit. JMHO.

 

[Pres100]

You should see what an HK gas gun with a fluted chamber does to brass! Pretty much the worst I have ever seen - but it can still be reloaded for plinking rounds.

 

[joshb]

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[Ron Blain]

What you are seeing is not unusual. If you look closely at the shell deflector on the rifle you will likely see brass embedded into it. A Google of "AR 10 fired slow motion" should bring up a few slow motion videos you can advance frame by frame. In a few of them you should be able to watch the cases extract and eject during which process the case mouths slam into the shell deflector. Extraction and Ejection are a pretty violent process when viewed in slow motion. There are changes which you can make, as was suggested springs and things and gas pressure but a change of ammunition and what you now have may surface again. Anyway if the rifle is shooting well as you mention I would not worry about changing anything. With a little care and patience, as mentioned, those cases can be reloaded.

Ron

 

[gunsandgunsmithing]

You should see what an HK gas gun with a fluted chamber does to brass! Pretty much the worst I have ever seen - but it can still be reloaded for plinking rounds.

Oh, I've seen it. Wouldn't want one, myself.

 

[Rsadams]

What you are seeing is not unusual. If you look closely at the shell deflector on the rifle you will likely see brass embedded into it. A Google of "AR 10 fired slow motion" should bring up a few slow motion videos you can advance frame by frame. In a few of them you should be able to watch the cases extract and eject during which process the case mouths slam into the shell deflector. Extraction and Ejection are a pretty violent process when viewed in slow motion. There are changes which you can make, as was suggested springs and things and gas pressure but a change of ammunition and what you now have may surface again. Anyway if the rifle is shooting well as you mention I would not worry about changing anything. With a little care and patience, as mentioned, those cases can be reloaded.

Ron

Not really unless you start shooting under powered ammo which may result in short strokeing.. Almost every AR with a short gas system will benefit from tuning.... Knowing if the gun is overgassed or under would be a start..

Most of them are over gassed to shoot cheap crap ammo which is under powered.. You don't really run into over powered ammo but you do under.. Especially in .223 carbine length gas systems they are normally over gassed and beat themselves up..

Most manufacturers are not going to add an h1 or h2 buffer becouse of cost not to mention it would defeat their idea of running an enlarged gas port for reliability.. Along those lines they are not going to add an increased power recoil spring either.. In the m4 platform I run a heavy buffer and stock power spring.. Good companies run an h-buffer but I believe colt has started shipping with an h1 now which increases lock time and well buffers better..

If you want to shoot cheap ammo and it short strokes simply use the stock buffer and spring, it doesn't get any easier to change back but I don't know why you would.. Good ammo is always better than cheap ammo.. There's a reason federal GMM and black hills cost more than tula... Also yes those cases will reload no problem , just run them through the die..