03-04-2022, 09:26 AM
montana Wrote:If all things are equal it sounds like your gas block port and barrel gas port are not lined up. Some gas blocks are made to fit against the barrel shoulder and others to fit with the hand guard retainer. This is why gas block ports can be drilled differently.. In any case it is best to measure for proper port alignment. It is easy to get the measurement from the gas port to the barrel shoulder and the same for the inside gas block port to the outside of the gas block to get proper alignment. If the gas block port and barrel port are lined up and it continues to short stroke, then the barrel journal could be undersized for the new gas block or vise versa. The barrel journal and gas block needs a fairly tight fit to prevent gas leakage.. Leakage can occur with a different gas tube, the gas tube fit in the new gas block or the gas tube fit to the gas key..If your Geissele gas block is the screw type, I would recommend dimpling the barrel under the gas port for your set screw. SLR makes an excellent jig for dimpling the barrel for proper gas block alignment. You have to order the correct size for a standard .750 barrel journal or the .625 used in many pencil barrels.https://slrrifleworks.com/750-dimpling-jig/ If the new gas block uses a pin, then the pin channel in the barrel and gas block pin hole may be different. This can cause the gas ports to not align properly.. The best and sure way to verify port alignment is with a bore scope.
Thanks for the response. I think the Geissele's gas port is too far forward (towards muzzle) for this journal. Meaning I cant move the block far enough towards the receiver to get it to align correctly. I suspect part of the port was blinded , so I just swapped back in what I know works. I have one of those SLR jigs, they are pretty slick. I think you may be on to something with the Geissele's pin hole not matching the barrel. However even with the pin in, the gas block is butted up against the "shoulder" so I dont see how that was the culprit entirely. Either way, I went back to what I know works and will go from there. Ill report results as soon as I can get back to the range. Thanks again!!