I just recieved two A-1 uppers both millitary Colt proof marked. The barrels are 20" (no marking) government profile. One has the 3 prong flash hidder the other has tha A-1 cage flash hidder. Does anyone know what twist rate these are or how I can find out? Thanks.........Kevin

head.gif

If they're military surp and unmarked, you can generally presume them to be 1/12, especially A1 style uppers in a light barrel contour.  To find out, use a cleaning rod with a patch in the holder.  Make sure the rod's tightened all the way down.  Pull the patch through and count the revolutions of the rod - make a mark with a pencil if you have to.

20" barrel: 1/12 = 1 2/3 revs, 1/9 = 2 ~1/4 revs, 1/7 = almost 3 revs.

Quoted: I just recieved two A-1 uppers both millitary Colt proof marked. The barrels are 20" (no marking) government profile. One has the 3 prong flash hidder the other has tha A-1 cage flash hidder. Does anyone know what twist rate these are or how I can find out? Thanks.........Kevin

1:12

Incompatible with anything heavier than 55gr