CMMG 22LR Bolt Group: Buffer & lower receiver wear

[A.J.P.]

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

The weld on the rear face of the bolt group is actually convex - which is what's beating on the buffer. I'm assuming that the buffer is slowly rotating upon this contact which is resulting in the pattern seen.

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.

Thanks for the comparison Brian - it appears from the feedback I've received that some owners experience this, whilst others have no issue - Ginger for example. Perhaps a difference in the internal dimensions of lowers?

how does your bolt return to battery then?

The bolt group's a self contained unit. The bolt travel is contained within the frame - in theory it shouldn't move once the upper and lowers are closed. In practice, it appears to be shifting under recoil.

I have consider refinishing the bolt group - I may cross that bridge in future.

[Blackstuff]

Grind/polish the back of the bolt group flat then and it should fix it

[Zilberbak]

Consider a Taccom .22 pressure plug have one fitted to my Raven. Made of high density plastic and puts a constant pressure on the bolt carrier. Sits between the buffer and the bolt carrier.

[A.J.P.]

Consider a Taccom .22 pressure plug have one fitted to my Raven

Thank you - the Taccom Pressure Plug has been recommended by several people as a solution. Does anyone know of any for sale/available in the UK?

[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.

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

The bolt and bolt group are quite different. Bolt runs up and down inside the bolt group on rails.

Buffer totally useless on mine. Removed It a few years ago.

[BamBam]

Mine has very slight buffer wear from the bolt weld, I only shoot standard velocity ammo.