Author Topic: Help me understand what happened with my 9mm  (Read 3690 times)

0 Members and 1 Guest are viewing this topic.

Offline Crawl

  • Full Member
  • ***
  • Posts: 223
Re: Help me understand what happened with my 9mm
« Reply #30 on: August 26, 2020, 12:19:16 AM »


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).

Offline Crawl

  • Full Member
  • ***
  • Posts: 223
Re: Help me understand what happened with my 9mm
« Reply #31 on: August 26, 2020, 12:23:58 AM »
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.

Offline Tok36

  • Hero Member
  • *****
  • Posts: 6146
Re: Help me understand what happened with my 9mm
« Reply #32 on: August 26, 2020, 03:03:54 PM »
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.
Will work for CZ pics! (including but not limited to all CZ clones)

Offline Crawl

  • Full Member
  • ***
  • Posts: 223
Re: Help me understand what happened with my 9mm
« Reply #33 on: August 05, 2022, 02:37:50 PM »
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


Offline RSR

  • Hero Member
  • *****
  • Posts: 4323
Re: Help me understand what happened with my 9mm
« Reply #34 on: August 07, 2022, 05:52:57 AM »
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.
« Last Edit: August 08, 2022, 01:07:49 AM by RSR »

Offline Crawl

  • Full Member
  • ***
  • Posts: 223
Re: Help me understand what happened with my 9mm
« Reply #35 on: August 07, 2022, 11:54:55 AM »
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.

Offline RSR

  • Hero Member
  • *****
  • Posts: 4323
Re: Help me understand what happened with my 9mm
« Reply #36 on: August 08, 2022, 01:47:20 AM »
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.