I've got a few JP builds under my belt.  I really like the MKIII handguard system - for the most part.  However, lately, some issues have come up.  I'm not sure if it's related to a potential QC issue, due to the craziness, or if it's something else.

Normally, when I'm installing the handguards, I can achieve about .010-.020" deviation at any measured point around the OD of the handguard, to the OD of the barrel.  However, with my latest build - which is a JP upper and handguard - I'm not able to get closer than .050-.060".  This is especially irritating for 2 reasons: 1) This handguard will host a clip on in front of the optic, 2) this handguard sleeves a suppressor.  And that's enough difference to be noticeable.

You can really only torque a steel screw in a piece of aluminum so much, before you're gambling with a thread failure.  This isn't a case for brute force.  For me, there appears to be an issue.  And since it's one of the longer handguards, the error will be exaggerated over the length. (the shorter handguards are literally never a problem)

Before I try to contact JP for the issue, just want to make sure that I'm not missing something obvious...

Thanks in advance.

Seems like there are very few who have actually built any of these...

Anybody out there specialize in JP builds?  Or run them exclusively for competition?  Know who to ask directly, that isn't JP? (it'd be interesting to know if there's some background info that JP might not be as likely to share)

This usually happens on most builds when the face of the barrel extension flange on the upper is not cut/machined square.  In reality, it’s the barrel that’s slightly out of alignment, not the handguard.

You could try lapping the upper, or just contact JP to see what they say if you don’t feel like altering the receiver.

You know, I was kind wondering about that.  For what I paid for this thing, that would be mighty disappointing.  Is it a known issue on JP, in particular? (I know of the issue on Mil-spec receivers)

I’ve never heard of it happening with a JP receiver, but then again, they’re not all that common, so that could account for that.

I’d probably just contact JP and see what they say.