JP Adjustable Gas Block isn't adjusting correctly...HELP!!

[Tedward]

Pull the gas block and measure the gas port with drill bit. Pretty sure you should have an .0935 port on a 24" pipe. There is a thread on here about port sizing, use the custom search engine, and I'm sure some others will chime in.

Well if all fails go the forum for direction and read the directions.

First went to square 1 and removed the JP LM BCG and used my original BCG, full mass, and removed the silent capture buffer and replaced it with a standard buffer and spring. Only difference now is the JP Rifle Adj. GB.

I expected more out of JP Rifles. The main issue was the gas port lining up. I used the rifle with my $45 gas block and it worked fine. So I upgraded to the Adjustable Gas Block to make it work smoother and it sounded like that’s what lots of guy’s do.

When I removed the AGB I measured the hole as recommended by ricsmall. Since the rifle cycled fine with the non adjustable gas block the size shouldn’t have been an issue. Since I don’t have a .0935 measuring tool, I checked the size with the drill bits I have on hand. The hole in the barrel was much smaller than 7/64” and my next size was much smaller. The hole on the gas block was 7/64”, the drill bit fit perfectly. I went ahead and opened up the hole on the barrel up to match the AGB since it can be shut down, being a little larger didn’t matter.

Second issue was the hole in the barrel and the hole in the AGB were not the same distance from the shoulder stop on the barrel. JP’s directions (had to look up and read on their web site) say to leave a .025 gap between the shoulder of the barrel stop and the gas block on military spec barrels. Well guess that measurement is wrong and the AR-Stoner needed a .052 gap between the AGB and the shoulder to make the center of the hole on the barrel match the center of the gas block hole.

So blowing air isn’t a sufficient process to make sure the holes line up.

Got it to work correctly, it cycles, feed second round and bolt hold open with my Fail Zero full auto BCG. Re-installed the JP Low Mass Bolt Carrier and it cycled correctly with hold bolt hold back on last round. Then I re-installed the Silent Capture Buffer Spring, still functioned correctly. Then I used the last few rounds of Wolf Ammo, it didn’t cycle. Glad I wasted it all on trouble shooting. Back to the Hornady VMAX and it still works correctly.

As a note, Wolf Ammo is less expensive, $17.99 per 20 but it is as dirty as my 22LR ammo. I will never save a few dollars and don’t recommend the ammo.

Moral to the story, measure EVERYTHING before assembly. This would have saved me $100 in wasted ammo. Now I can sight in my scope tomorrow. Fathers Day is going on today, Dad’s up from Florida.