Grip screw problem

[Slick371]

I'm building an AR using a Noveske upper/lower set. I'm trying to install a Magpul MIAD grip but can't seem to get the grip screw tight. I have tried removing the grip and installing the screw w/o it. I've also tried using both the screw that came with the grip and the one that came with my Daniel Defense LPK (The DD screw is slightly shorter). Neither will tighten all the way. Should I find an even shorter screw or use washers to shim? I don't want to strip the threads on my lower but I also don't trust shims.

Thanks for your help!!

[Constructor]

You could chase the threads, there should be a lock washer unless it had the screw with blue locktite on it, it doesn't take up much room but not sure how much you are talking about. Any hardware store should have a shorter screw if you can't chase the threads.