proper pistol gas port diameter

[320pf]

Well I finally had a chance to check the gas port diameters on the two 300-221 Fireball barrels with a set of pin guages. Here are the results.

The Olympic Arms 16", 1:8 twist stainless steel barrel; the action cycles for both sub-sonic loads as light as 165 gr and super sonic all rounds without having to adjust the gas block. The gas port is about 0.5" closer to the chamber than the standard ar15 pistol port. The port diameter is 0.082"

The Noveske 16", 1:7.5 twist stainless steel barrel; the action does not cycle light (165 gr bullets) sub-sonic loads. I have not tried sub-sonic loads with heavier bullets. I have shot super sonic loads in the following bullet weights, 110,125,150,155,165,168,175, and 180. All cycle the action. This barrel will shoot 0.5' groups all day long. The port is in the standard pistol position and the port diameter is 0.071".

So in conclusion, if you are building an upper with the gas port in the pistol postion, you will want a gas port to be 0.082" in diameter

I hope this helps

320pf