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Posted: 10/7/2004 4:28:13 PM EST
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

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Link Posted: 10/7/2004 9:24:25 PM EST
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.
Link Posted: 10/7/2004 9:55:06 PM EST

Originally Posted By militiamedic:
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
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