My 300blk SBR CMMG will not fire

[rOmiLaYu]

Triathloncoach

 

[Dirty J]

All AR mags, when loaded, will have some level of difficulty beating seated with the bolt forward as the top round in the mag is pressing into the bolt carrier. With the bolt back or the upper off, insertion is easier.

That's VERY lower/parts kit/mag dependant. Milspec tolerance stacking.

Ive got rifles that have difficulty seating full mags and I've got some that'll take a full pmag without issue - minimal effort required.

You can always download the mags on the ill fitting rifles...

Or I've also played around with doing some fitting on the mag catch to lower the magazine a few thousandths. Just have to be careful to not go so low to prefer the BCG from picking up the next round.

 

[Triathloncoach]

It's a factory CMMG. The magazine catch has been a nuisance for a while but the gun always fired. Now it goes click on the cartridge. I always shoot it suppressed.

 

[StuP]

Is there a mark on the primer ?

 

[Dirty J]

Either the gun isn't going in to battery, has a broken firing pin or hammer spring