CMMG 22LR Bolt Group: Buffer & lower receiver wear

[A.J.P.]

Hi guys,

I'm hoping to pick your brains. My new (to me) custom 22LR AR15 has some odd wear on the buffer and lower receiver. It's had approximately 350 rounds through it before I bought it - and I've just fired another 600. What would be your thoughts - is this type of wear normal?

The lower' s a Noveske Gen 3 and the upper's a VLTOR MUR. I had absolutely no reliability issues during firing the 600 rounds - barring one related to the magazine. The rifle's also very accurate. I'm using a Bettermag Adapter if that could possibly be relevant.


Some images before cleaning:







And after:








It appears that the weld on the rear of the CMMG bolt group is beating up the buffer. I'm not too worried about this - the bolt group has no appreciable wear, and I presume it'll just strike the buffer until it's worn a groove into the buffer's face.

I'm more concerned about the wear to the lower receiver itself. It appears that the tang of the carrier, at the top, were the spring connects, is hitting the rear of the lower. Is this normal?




Thank you in advance to all who reply,

Adam

[Grantd]

Just checked mine (all CMMG) and after 1700 ish rounds isn't as bad. I've a small divit on the buffer tube and an outline mark of the tang. The weld on my bcg doesn't protrude as much as yours, I also don't run the forward assist plastic piece but upon checking mine it wouldn't reduce the bolt travel anyway.

I have run a mixture or of subs and cci's so maybe it may be an ammo thing.

[safetyfirst]

How odd. On mine the bolt group never touched the buffer. In fact I've removed the buffer, you can too, not required.

The bolt assembly clicks into place round the barrel extension and will not move backwards. Once the bolt is in you can clearly open and close the upper receiver and there's a gap between the back of the bolt and the buffer. This gap should not change during firing.

I removed my buffer and buffer spring a few years back.

Mine is a stock CMMG upper and lower. Original, not MK3.

My rifle is about 35,000 rounds in or something ridiculous.

[BamBam]

I only use standard velocity ammo, my buffer and bolt have slight marks from pressure against each other.

You can fit a butt plug if you're concerned. https://taccom3g.com/product/22rf-insert-pressure-plug/

[safetyfirst]

I think those are designed for conversion kits. The dedicated .22 uppers capture the bolt assembly. Have I missed that were talking about a conversion bolt?

[A.J.P.]

I think those are designed for conversion kits. The dedicated .22 uppers capture the bolt assembly. Have I missed that were talking about a conversion bolt?

No - it's a dedicated .22LR bolt group and barrel (with extension).

There's still a small amount of forward play in the bolt group - even when it's firmly attached to barrel extension. That is, once the barrel collar has clicked onto the extension, pressure on the rear of the bolt group can move it forwards ever so slightly, spring pressure then returns it to rest.

I'm presuming that under recoil, the rearward movement of the bolt is slamming the carrier's tang into rear of the lower and the carrier's weld into the buffer.

[Blackstuff]

The wear pattern is bizarre, both appear to be concave and on both contacting surfaces, as if there is something being stuck between the two I would've just expected the outer ring wear pattern that is also shown.

I'd be tempted to polish both surfaces flat and see if it keeps happening, or as suggested fitting the plug.

[Ginger]

Hi Adam,

I have a Spikes and it uses basically the same kind of bolt (it has a spikes twist, different collar & firing pin), and I haven't seen issues like this on either of my Spikes which are 7+ years old and have x thousand of rounds through them

[breacher]

Bradley Arms .22 here and it uses the same sort of part that you have shown wearing. No wear marks at all here - on that part or on the buffer.

[bradaz11]

How odd. On mine the bolt group never touched the buffer. In fact I've removed the buffer, you can too, not required.

The bolt assembly clicks into place round the barrel extension and will not move backwards. Once the bolt is in you can clearly open and close the upper receiver and there's a gap between the back of the bolt and the buffer. This gap should not change during firing.

I removed my buffer and buffer spring a few years back.

Mine is a stock CMMG upper and lower. Original, not MK3.

My rifle is about 35,000 rounds in or something ridiculous.

how does your bolt return to battery then?


As to the op, If you clean the weld on the rear of your bolt, it should sort it out