Question for the AR guys

[john 800]

Are both uppers the same barrel length? If not, what are they and which exhibits which problem?

The one that is locking up is a 16” the one that doublefeeds and stovepipes is an 18”

 

[john 800]

To update the situation: I concentrated on the one was stovepiping and double feeding for now. I tried another lower and it acted the same. Next step was a jp adjustable gas block, installing that made it not cycle regardless of where the gas adjustment was set. Other than double checking gas port alignment do you have any suggestions? I am at a loss.

 

[Knotwild]

It sounds like you have a few ARs. If possible, for education purposes, I would try swapping in a different bolt carrier. If that didn't work, I would part out the uppers and buy some new ones - with a little better reputation. I have 4 complete guns I built myself that work. And, I know you can't just swap bolts between a Grendel and a 5.56.

 

[dellet]

Try some name brand ammo.

No direct knowledge of the Druid Hill, but every time there is an ammo and component shortage a bunch of small manufacturers pop up and forums are flooded with “my AR won’t cycle threads”

Might be related, might not. But my default is always quality factory ammo, unless it’s my well established loads.

 

[Herzo]

Stovepiping and double feeding suggests under gassing. That is the 18", I would check the diameter of the gas port. I would expect something around 0.078". An adjustable gas block will not help that situation.

The 16" could be over gassed. In that case the adjustable gas block could rectify the situation. Double check that the hole in the gas block aligned with the gas port in any case.

 

[Old Navy]

I'm with finding a known good lower. I find it's a lot easier to have at least one part that's known to work.

If the new uppers don't work with a known good lower, I'd call the vendor for help. They know them best.

Right on!

 

[Kevin1990]

I'd check the gas port size with pin guages, which I myself dont even have. I hate to be that guy, cause I buy budget items all the time, but BCA has a pretty horrible reputation. I've shot several friends BCA uppers, and they usually don't make it through a range session without some kind of problem.

Keep is updated though. Im curious to know what the problem is.

 

[Walt Krafft]

You can check the port size, but what size is it supposed to be for a 6.5 Grendal with; x length barrel, y buffer and spring, and z ammo? I have been down this rat hole.

 

[john 800]

Another update.
I didn’t get right back to digging into these because of stupid work being busy. But The 16 one appears to have a tight chamber, loaded rounds are tight in the neck (going by scuff marks on a new nosler loaded round, if i try to chamber a go gauge it chambers but is really tight extracting it. Rather than rework the chamber I just ordered a barrel. I should have just bought a quality piece to begin with. The barrel i ordered is an 18 with mid gas tube, so if that works maybe itbwill tell me something about the size ofvthe gas port on the other one.