Out of spec Picatinnys can create mounting problems, and they are out there.

Friend bought Leupold quick-mounts (has levers for tightening to base) and was unhappy with them not staying tight. I have enough faith in Leupold that they would not sell an inferior product. I bought them from him for a price which gave him some money back and saved me some.

I tried them on an AR15 handle converter. Be darned, tightened them on the Picatinny and they rattled. Noting the mounts were as closed as they can go, I measured the rail width. It measured .818". It should be in the vicinity of .835". Don't know yet if that was my friend's situation, but suspect it may be and I will tell him of my find.

I went about measuring 11 Picatinny bases, curious as to their consistency. Some were in a .832-.837 range. One 45 degree offset base was .817. A handle conversion with forward extension was .849 at the handle, and .833 at the forward extension. Four smaller accessory picatinny bases measured .826, .826, .829 and .835. An old Weaver base measured .837, and the bases factory-installed on the T/C Compass measured .833".

The question of the mounts refusing to remain secured remains open, waiting for the test under fire. I have seen videos of long-range shooters using mounts with lever tighteners, so it appears to be an accepted design.

Purpose of this post...if anyone is having trouble with accessories refusing to remain secured, try measuring the base.