Help me understand what happened with my 9mm

[Crawl]

This isn’t unusual in a blowback 9mm AR but surprising from a radial delayed setup, that’s the point, not to fire unless it’s locked.
You did right to send it back, a potentially dangerous situation.

Personally, I’d ditch the Armscor, I’ve not been impressed with any Armscor ammo. For me, brass Blazer 115 gr. Is just as cheap and more consistent, and for a few pennies more there’s much better options.

I think if I spent the $$$ for a CMMG I’d buy better ammo like MEN 124 gr. NATO. Which is far from the best, but cheap enough for cheap plinking.

I’d also avoid any aluminum cased ammo, IMHO just too soft for unsupported chambers. I have several blowback carbines that choke on Blazer aluminum but run fine on any brass or steel case.

As I stated originally, it isn't Armscor ammo, it was their brass. Besides that, it also happened with every brand I used (including Blazer, which is also cheap).

[Crawl]

Update:

Tested the rifle this weekend at the range (after firing about 800 rounds through an MP5 switching between full and semi auto), and the result is that CMMG's replacement bolt seems to have fixed the problem.

The recoil compared to the MP5 is a little greater, but it's still better than direct blowback.

I happened to be shooting next to a guy who has the same CMMG radial-delayed blowback gun, and he has had zero problems with his.

So far, so good. Seems like the new extractor fixed the problem. I'm certainly not knowledgeable enough to understand how.

[Tok36]

Update:

Tested the rifle this weekend at the range (after firing about 800 rounds through an MP5 switching between full and semi auto), and the result is that CMMG's replacement bolt seems to have fixed the problem.

The recoil compared to the MP5 is a little greater, but it's still better than direct blowback.

I happened to be shooting next to a guy who has the same CMMG radial-delayed blowback gun, and he has had zero problems with his.

So far, so good. Seems like the new extractor fixed the problem. I'm certainly not knowledgeable enough to understand how.

I do not understand ether but i am glad that you got it fixed. Thank you for the follow up.

[Crawl]

Catching up on old threads today.

Seems like the issue all along (besides parts that break easily) is that I was using a buffer with inadequate mass.

Sent from my SM-G986U using Tapatalk

[RSR]

Catching up on old threads today.

Seems like the issue all along (besides parts that break easily) is that I was using a buffer with inadequate mass.

Sent from my SM-G986U using Tapatalk

Yes, you want to go heavy with blowback buffers and also consider heavier springs, such as those made by springco. 

FWIW, Vltor's A5 buffer system is also something that helps control 9mm recoil and increase function/reliability - if you don't need a super short gas tube/length of pull.

[Crawl]

Agree with all of that. I knew what to do when I built it, but I wasn't mentally processing what was happening at the time!

I recommend sprinco springs too, and I always change springs before the buffer weight gets changed.

[RSR]

Agree with all of that. I knew what to do when I built it, but I wasn't mentally processing what was happening at the time!

I recommend sprinco springs too, and I always change springs before the buffer weight gets changed.

Yeah, I didn't even think about springs not knowing much about how CMMG's recoil system on these guns works.  Apparently, not as different practically from a standard blowback 9mm AR.

Springs are more about how much braking you want while bolt cycling (have to up power if upping buffer weight) and ensuring sufficient force to reliably chamber a round.  Why generally you go w/ strongest spring that allows your bolt catch to activate with your weakest ammo (recognizing that bolt catch may not work if using weakest ammo when it's super cold, but should still function)...

Springcos are rate for what, 50k rounds or so? -- That's more than the lifetime of your barrel?  What I like about them is you only need to replace during barrel changes vs a lot more spring changes with milspec springs and their 5k service interval.

Buffer weights are more about increasing dwell time and reducing overall felt recoil (and not just recoil duration) and generally are more important to proper function.

Me personally, while I start with a Springco Blue Spring or XP equivalent (Geissele braided, Tubb flat, etc.) for 14.5-16" DI AR15s, and H1 buffer w/ midlength and H2 with carbine and go from there -- both in carbine buffer tubes.  A5 tubes are a whole different formula.

[Rex2022]

I know this is an older thread, but I'm having similar issues with my CMMG Banshee. 
 

I contacted CMMG by email on 12/25/22 about the Banshee firing out of battery. They responded on 12/29/22 and on 12/30/22 via email and their suggestion is to try different ammo and encouraged me to continue to fire this firearm even though I have explained to them that I believe there is a safety risk in doing so. I further explained that it’s not an ammo issue and but rather an out of battery issue. Regardless if the ammo is in spec or not, the firearm should prevent the round from firing if out of battery.

Attached are pictures of that I had sent CMMG. On 12/30/22, I requested CMMG either replace the firearm or pay me for the purchase price (I would surrender the firearm to CMMG). No response! I emailed them again on 1/6/23 and I haven’t received a response from them from that request either. I have called CMMG (660-248-2293, option 1) on several occasions since 1/6/23, including this morning, but it always goes to voicemail and as stated on their email they encourage all customer service questions being emailed to them.

I purchased this firearm in September of 2022. The firearm immediately had feeding issues with all kinds of ammo. The rear of the bottom lugs on the bolt were striking the case mouth of the loaded round in the magazine. As the bolt travelled rearward from firing, the rear of the bottom bolt lugs struck the case mouth of the loaded round in the magazine and turned it cockeyed in the magazine. When the bolt moved forward after cycling it pushed the cockeyed round out of the magazine and it failed to feed in the chamber. This happened time after time. CMMG had the firearm for about 6 weeks and resolved the feeding issue by replacing the bolt.

Does anyone have any opinions or suggestion on the matter?

[Crawl]

The solution is a heavier buffer. It's SUPPOSED to run with a carbine buffer, but it needs an H2 at least.

[Rex2022]

The solution is a heavier buffer. It's SUPPOSED to run with a carbine buffer, but it needs an H2 at least.

I'm having erratic ejection too. Some of the cases dribble out as it is. A heavier buffer will only create additional ejection problems. The banshee regulates the weight through the carrier by adding weights, which I have but not installed.

If the firearm fires out of battery, then adding more weight to either a buffer, or in my case, to the carrier would not solve the problem. Granted, in some instances it may reduce the chance from soft feeding or bolt bounce, but it can't cure completely the out of battery situation. That, in my opinion, would be mechanically impossible.

Regardless of the reason, it should never be able to fire out of battery. There's a lot of reasons why the banshee could go out of battery, like debris in the chamber, out of spec round, etc.

[Crawl]

Not sure why you think a firearm SHOULD prevent it from firing out of battery. A guy can over gas and under spring a gun and cause unsafe situations. But I do agree that it is clearly not working as advertised. Not saying yours SHOULD work like mine. There likely is some other issue. The Banshee may very well be a poor design, but mine is a dream to shoot when I buffer it adequately. They said it is designed to work with a carbine buffer...that being obviously untrue about mine indicates to me that CMMG is not necessarily as reliable as someone like AR15 Performance. 

Using out of spec ammo I, by definition, asking the gun to deal with something it wasn't built for.

You may be using weaker ammo, you may not. It likely isn't your fault that it has issues. They replaced my bolt, and it didn't fix my problem. A heavier buffer and spring did fix it. It cycles even with my Minor PF handloads.

[Rex2022]

Not sure why you think a firearm SHOULD prevent it from firing out of battery. A guy can over gas and under spring a gun and cause unsafe situations. But I do agree that it is clearly not working as advertised. Not saying yours SHOULD work like mine. There likely is some other issue. The Banshee may very well be a poor design, but mine is a dream to shoot when I buffer it adequately. They said it is designed to work with a carbine buffer...that being obviously untrue about mine indicates to me that CMMG is not necessarily as reliable as someone like AR15 Performance. 

Using out of spec ammo I, by definition, asking the gun to deal with something it wasn't built for.

You may be using weaker ammo, you may not. It likely isn't your fault that it has issues. They replaced my bolt, and it didn't fix my problem. A heavier buffer and spring did fix it. It cycles even with my Minor PF handloads.

“Not sure why you think a firearm SHOULD prevent it from firing out of battery.”
To me, that gets into a whole philosophical argument on whether a manufacturer has a moral, ethical, and legal duty to protect the user from potential harm from their own design. I think, at least to some extent, they do. Again, it may not be an out of spec round that causes an out of battery issue. It could be from things like debris in the chamber or even bolt bounce (OOB while rapid firing), etc.
If CMMG believed that a heavier buffer would solve the problem, then they would’ve said it in their response on the 12/29/22 and 12/30/22 reply, but they didn’t. They simply blamed it on ammo and told me to continue to shoot it with different ammo.

“A guy can over gas and under spring a gun and cause unsafe situations.”
I agree, but now the user has altered the firearm. In doing so may relieve the manufacturer from some or all of any liability.