03-24-2022, 06:02 PM
mtnlvr Wrote:I'm guessing you can lock the slide back by simply using the charging handle and an empty mag / chamber?
If you have a good, functioning upper I'd try swapping it onto his. If the bolt doesn't lock back start looking at the recoil system. If it does lock back, it's likely an issue with the gas system.
Yes, the gas port could be undersized, but it's more likely that the block is out of alignment and would need to be loosened from the barrel and realigned. It's not to difficult.
With your good upper and his upper removed from their lowers, you can also compare how easily you can blow ait through the gas tube. I've used a section of vinyl tubing to extend the gas tube so I can blow into it. That may help you determine the block is out of alignment with the port.
There are plenty of tricks to help getting the port aligned. A piece of dried spaghetti is a good one. Toothpick works too. Just make sure you get it all back out.
If you end up taking the gas block off, measure the diameter of the port. That's best done with gage pins but you probably done have that. Next best is probably drill bits...find the biggest drill bit that goes through to the bore...by hand. You'd likely need a set of numbered drill though, not just in 1/16" increments. A caliper works OK too, but doesn't reach all the way to the bore to verify the hole goes as far as it should. At least visually make sure the hole looks clean to the bore.
You don't even need to take the muzzle device off or gas block completely off the barrel. Just loosen to slide it towards the muzzle. Now depending on your handguard design, that might get in the way.
There's really not a lot too it.
Of course if it's new, the manufacturer should fix it too under warranty, but then he's going to be without it for a bit.
The lower that we are using was just on his .223 upper and everything works flawlessly. Full, lock back of the .223 bolt.
I have since read several instructions from several manufacturers and most all of them say to start one full turn from completely closed and open a half a turn per shot till it locks back. I'm going to give it one more go like that and then I am giving it back to him to have someone else dig deeper into it or he can ship it back to PSA for them to look at.
lazyengineer Wrote:Fully remove both screws. Then insert your Allan wrench into the cavity to figure out which screw partially blocks the gas path, and which screw engages the other screw to hold it there.
Be aware such screws do tend to walk out btw. If they don't carbon lock.
Then track you screw position based on how many revolutions out from fully closed and bottomed out. Note that there will be a sweet spot where 1/8 turns matter. And everywhere else where it doesn't matter at all.
I definitely have the screws figured out as one of them has the milled detents in it and the other would have completely closed off the gas since I had the adj screw unscrewed so far if I had them backwards. Believe me, the thought crossed my mind by the time I had shot the 8th shot and the bolt was not locking back completely yet.