
Originally Posted by
patrolman
Alright folks,
Measured eight different bolt carriers out of Colt M4A1's today. Four of the eight I.D.s measured .5275". The rest varied from .5249 through .5280. Regardless, it looks like a difference of slightly over 20 thousandths compared to the .503" of the McFarland rings. That would explain the looseness.
Well, unfortunately, it looks like a no-go on the McFarlands and these M4A1 carriers unless I'm missing something.
Again, thanks for the info and advice, folks.
?????
Remember that the carrier bore has two chambers,and a port at the very back for the bolt tail which works as a mechanical seal basically.
The first and larger chamber at the front of the carrier bore is where the bolt bearing band resides.Then you have a step transition into the smaller rear chamber in which the gas rings reside.
I checked some carriers at the front chamber and all are around .5280"-.5300"+/- throughout a mixed bunch from LMT,Armalite,DD,BCM and Spikes..Unfortunately I do not have a bore gauge small enough to fit the carrier bores at the moment,and a caliper aint gona reach..
I cant find any internal dimension of the carriers online,but if I were to take a shot in the dark I'd say the gas ring or second chamber of the carrier bore will be close to my used McFarland rings which have a "fit like a glove" feel...and that being roughly or slightly smaller I.D than the .4970"-.4985" my rings measure.
So if your measuring the front chamber to gauge gas ring fit,it has nothing to do with what the gas rings will do.If your carriers have a single size chamber all the way in,then you have a major malfunction.
Last edited by Blankwaffe; 03-02-10 at 07:07.
Reason: ETA
Glock Certified Armorer
Armed Protective Services II
Bookmarks