I can't seem to find the proper dimension for the A2 gas port (hole in the barrel) in my reference collection.

I built my son an A2, using a PSA premium upper.  It short strokes pretty regularly currently.  The PSA BCG that was originally in the upper has a sheared gas key screw, but it still won't function properly with a different, known to work bolt carrier I had laying around.

I'm also waiting for a new buffer spring, as the one in the gun seems too strong.  It requires much effort to retract the charging handle.  But if that won't fix the problem, I want to measure the gas port diameter before I do anything else.

20" government .093"

It's harder to find the gas port size for a 20" A1.  No one seems to know that information!

Length Diam   Min Port   Max Port


20.00    0.625  0.086         0.093



20.00   0.750  0.093         0.096



From a post on the practical machinist.

http://www.practicalmachinist.com/vb/gunsmithing/gas-port-location-235116/



I just moved to .125 on my 16" rifle gas dissipator barrel.