CMMG 22 Conversion Problem.....

[jcountry]

I have a CMMG kit which I have used in a couple different ARs.

Got one I'm trying to us it in now, and the damned thing won't fit. Stays about 1/8" too far aft. Looks like the lugs of the barrel are a bit different from what I'm used to seeing.

Anyone seen this?

 

[Hayata]

I've only tried mine in one AR and everything was fine. What a clever concept!

Everything in place/where it should be on your insert?

 

[jcountry]

I've only tried mine in one AR and everything was fine. What a clever concept!

Everything in place/where it should be on your insert?

Yep.

Far as I can tell....

I have a feeling this AR lug assembly is a little shallow.

 

[ATLDude]

Which kit do you have?

I have 2 from CMMG. One with a brass looking bushing when it goes into the chamber and an older one from about 10yrs ago without the bushing. They have worked flawlessly in any AR I've put them in.

Does it fire?

 

[rockdawg]

Check the chamber for possible carbon build up. Never had a problem with mine.

 

[jcountry]

Which kit do you have?

I have 2 from CMMG. One with a brass looking bushing when it goes into the chamber and an older one from about 10yrs ago without the bushing. They have worked flawlessly in any AR I've put them in.

Does it fire?

Nope.
Can’t even close the upper.

 

[fattboyzz]

I had this problem with a PSA barreled upper . It was to snug for the 22lr bolt group to seat all the way. I could see where the lugs were preventing the assembly from seating . It left tiny little marks on the front of the brass bushing.

 

[jcountry]

I had this problem with a PSA barreled upper . It was to snug for the 22lr bolt group to seat all the way. I could see where the lugs were preventing the assembly from seating . It left tiny little marks on the front of the brass bushing.

View attachment 2420470

That's exactly how I would describe it.

I'm gonna call PSA.

 

[jcountry]

I test-fit the conversion in another upper, and it works just fine.

After a more-careful look, I can see that the clearance into the throat of the chamber is wrong. The diameter between the lug channels is about 5 thousandths or so too narrow.

Never had trouble with PSA before, but this is clearly bad machining.

 

[toobaroque]

Mine run fine in all my PSA uppers. Crap accuracy because of the twist rate so I've dedicated a pistol upper to it. I get 5" accuracy now at 100 yards and 10" barrel.