Non-milspec upper

[Sasquatch]

I cheaped out in my lightweight AR build and got a no-name slick-sided upper (Durkin). It was significantly less than the Aero slick-side, and I thought it would be ok.

It isn't. The barrel won't seat. It appears it could be a couple of things- the first is that dimensionally the upper is shorter than a mil-spec upper. Looking at where the barrel pin stops, there's still a gap as the barrel seats against the threaded part of the receiver. When I put a barrel nut on it, it screws in fine. When I put the barrel nut in, it stops well short of seating near the receiver. It's the right torque- so who cares, right? Except, when assembled, there's a noticeable gap between the handguard, as well as the rail between it and the upper. On the inside of the receiver, it looks like the barrel isn't fully seated (and it looks like the M4 feed ramps are wrong on the upper as well.


What to do besides throw this away? (Vendor wasn't a help- won't be ordering from him again).

I'm thinking of machining down the face where the barrel seats to close the gap on both the handguard and the inside of the receiver? Thoughts?

 

[JBoyette]

Might be tight as hell. Once torqued how does it head space? The visual of the barrel ext, might not be true. Secondly do not assume its the upper. You "could" have a bad barrel ext. So I would test a second one. But again. Head spacing tells the story. With a go / no go gage. I do agree that Its appearing the upper was cut short. If so, I see an AR9 in your future.

 

[JRHorne]

Throw it away. Aeros or used uppers are too cheap.

 

[Sasquatch]

The barrel seated perfectly on another upper as did the nut and handguard. The only variable is the upper. I should get a headspace gauge, but they're proud of those (and one of my ARs is a colt which apparently has a different set needed).