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.