Scratching/gouging on brass, need help!!

[damon32382]

Got a brand new AR style CMMG Banshee chambered in 45ACP. Love this thing, but the spent brass casing are getting scratched and some gouges in them. It's not gouging completely through it by any means, but it's enough to where it's making me think it's too much.
I reload, otherwise this wouldn't be much concern. I know this Banshee isn't a typical AR, but it's still built very similar. Can anyone tell me how to fix this problem and what's going on?

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[terdog]

Have you tried other buffers? My 10 came with 2.
Also, call CMMG and see what they say.

I luv mine.

 

[Member 34319]

Pictures would help. Likely the cases are still loadable.

The CMMG doesn't use a regular fixed ejector. It uses a plunger ejector like the regular 556 chambered AR does. This means the empty is pushed in to the side of the barrel extension and or receiver as it it traveling rearward (after fired) until it nears the ejection port where it leans out until the bolt goes rearward enough that the spent case leaning out of the ejection port meets the back corner portion of the ejection port and smacks into it. Finally releasing it from the extractor.

Regular blow back guns have a nice blunt ejector that hits the butt of the spent case as it's traveling rearward while cycling. Usually this takes place mid cycle to allow good timing on the bolt to ejection port.

So the CMMG ejection is a little bit harder on brass. After shooting mine a ton, I'm considering it the worst part of the design.

 

[terdog]

Interesting. My brass comes out perfect ...

 

[damon32382]

Have you tried other buffers? My 10 came with 2.
Also, call CMMG and see what they say.

I luv mine.

I have called CMMG, but it was unrelated in a way. They were cool enough to swap out my micro rip brace for a standard size one. This involved changing out the buffer tube also I guess. But they put in a 3 oz. stars buffer on accident. They sent me an H1 after, but I put in a H2 with a 15% extra power carbine spring. Helped a ton on recoil and my bolt not getting the crap beat out of it, but I'm still getting gouged brass. Other than that, I love mine too. And my brother has the 10mm Banshee also, runs like a champ and no brass gouging.

 

[damon32382]

Pictures would help. Likely the cases are still loadable.

The CMMG doesn't use a regular fixed ejector. It uses a plunger ejector like the regular 556 chambered AR does. This means the empty is pushed in to the side of the barrel extension and or receiver as it it traveling rearward (after fired) until it nears the ejection port where it leans out until the bolt goes rearward enough that the spent case leaning out of the ejection port meets the back corner portion of the ejection port and smacks into it. Finally releasing it from the extractor.

Regular blow back guns have a nice blunt ejector that hits the butt of the spent case as it's traveling rearward while cycling. Usually this takes place mid cycle to allow good timing on the bolt to ejection port.

So the CMMG ejection is a little bit harder on brass. After shooting mine a ton, I'm considering it the worst part of the design.

Really appreciate the detailed reply, thank you. Makes sense the way you explained in what's happening. As I mentioned in another reply, I've put in a H2 buffer and a 15% extra power spring because it definitely needed it regardless. But also read that it could help mitigate the brass gouging, but no luck. Am I stuck with this problem? I've read about people sanding down, or filing things so smooth out sharp edges off either the bolt or the star/breech area. But I don't know if I should attempt that.

 

[damon32382]

Interesting. My brass comes out perfect ...

Is yours chambered in 45ACP also?

*edited* Just noticed you mentioned you have a 10mm. Never mind

 

[JuglansRegia]

Well, anything that touches your brass can damage it. So the feed lips on the magazine. The underside of the bolt carrier, the feed ramps and locking lugs on the barrel extension and finally the shell deflector. Without seeing the damaged brass that is all I can tell you.

 

[damon32382]

Well, anything that touches your brass can damage it. So the feed lips on the magazine. The underside of the bolt carrier, the feed ramps and locking lugs on the barrel extension and finally the shell deflector. Without seeing the damaged brass that is all I can tell you.

I've heard of if that with the feed lips on the mag, especially brand new Glock Mags which is what I'm running. I will get you a pic here shortly.

 

[damon32382]

 

[damon32382]

 

[damon32382]

Well, anything that touches your brass can damage it. So the feed lips on the magazine. The underside of the bolt carrier, the feed ramps and locking lugs on the barrel extension and finally the shell deflector. Without seeing the damaged brass that is all I can tell you.

Posted some pics. Wondering if there is a burr on locking lugs? I don't know...

 

[JuglansRegia]

Those are from the splines on the barrel extension, you'll have to sand off the sharp edge with a needle file or something. Usually it happens after the round is fired, the ejector pushes the brass to the right and it drags along those sharp edges as the carrier pulls it out of the chamber.

 

[damon32382]

Those are from the splines on the barrel extension, you'll have to sand off the sharp edge with a needle file or something. Usually it happens after the round is fired, the ejector pushes the brass to the right and it drags along those sharp edges as the carrier pulls it out of the chamber.

Ok, thank you for taking a look at that and for the info. I'm guessing I need to feel around for any burrs??

 

[damon32382]

Those are from the splines on the barrel extension, you'll have to sand off the sharp edge with a needle file or something. Usually it happens after the round is fired, the ejector pushes the brass to the right and it drags along those sharp edges as the carrier pulls it out of the chamber.

Where on that barrel extension do you think it needs filed? Since the extractor is pulling at the 3:00 position, somewhere in there?

 

[JuglansRegia]

Where on that barrel extension do you think it needs filed? Since the extractor is pulling at the 3:00 position, somewhere in there?

Yup, somewhere around 3 O'clock, I would mark and empty up with a sharpie, chamber it then slowly pull the charging handle back while observing.

 

[damon32382]

Sounds great, thanks again. Sorry to bug you with another question, but is it also possible that after a while, would those sharp edges work themselves out with a number of rounds through it? I'm not going to wait for that to happen, but I'm just curious.

 

[JuglansRegia]

Sounds great, thanks again. Sorry to bug you with another question, but is it also possible that after a while, would those sharp edges work themselves out with a number of rounds through it? I'm not going to wait for that to happen, but I'm just curious.

You'll go broke waiting for brass to wear down 4150 or what ever that steel is.

 

[Member 34319]

Looks decent really.

If you were to clean that with stainless media, it would likely be completely unnoticeable after.

I want to say that is from the barrel extension as it looks like the right size of a lug.

I'd say shoot it. Things smooth out over time.

 

[damon32382]

Looks decent really.

If you were to clean that with stainless media, it would likely be completely unnoticeable after.

I want to say that is from the barrel extension as it looks like the right size of a lug.

I'd say shoot it. Things smooth out over time.

Ok cool, I might try smoothing some of it out if I'm brave enough, but hope it works itself out if I don't. Thanks