Upper Receiver Barrel Assembly HELP

[Aaryk]

Hi,

I had the guys over a Parallax Tactical put together an upper receiver for me since it was my first build and I lacked the proper tools, namely a vise block. Anyway, I supplied them with the upper, barrel, nut, muzzle brake and handguard. They took it to the back and finished in about 20 minutes. Something to me looks weird though when I got it back - the junction where the barrel nut meets the upper has a gap and there is about 1/2 a centimeter of the gas tube that is exposed. I didn't notice this until I got it home.

Is this normal or okay?

I see other rifles/builds where there is no gap at all. Did they not torque enough? I assumed they'd know what they were doing and there must have been a reason to leave the gap like that. I'm not sure...that's why I'm asking everyone. Also wondering if it's the parts not being compatible or anything.

Should I take it back and have them adjust it more? Or it is what it is?

And if it helps, the build is a based off a Mk12 Mod 0 SPR. Upper receiver is Aero Precision. Handguard is Gen III Forearm by PRI.

Thanks!

[Aaryk]

Here is a pic for reference:

[PuppY_K1ck3R]

Doesn't look right seems like the barrel nut isn't tightened down at all.

[ar15barrels]

As long as the handguard is solid, it is fine.
That's just how some rails are...