03-24-2022, 12:24 PM
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.
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.