Upper/Scope Mount Mismatch

[mdmp5]

2 things in one day for me. I should play the fucking lottery. Anyway, in addition to my handguard debacle, I went to mount my 1 piece mount on a new upper, torqued it on, and the thing fucking wobbles like you cannot believe. Makes absolutely no fucking sense. If I put this mount on my other picatinny rails, it seems to fit. Conversely, if I try another mount on this upper, it fits totally fine. I don't want to name the manufacturers of either piece, because I don't want to give them any bad press, especially because I can't figure out which piece is out of spec. My question is, is it possible to have 2 functional pieces (a picatinny rail and a scope mount) that only malfunction when pieced with one another?

 

[demolitionman]

"The Picatinny locking slot width is 0.206 in (5.23 mm). The spacing of slot centers is 0.394 in (10.01 mm) and the slot depth is 0.118 in (3.00 mm)."

Put some calipers to work and find out.....

 

[mdmp5]

I have the NATO spec sheet here. Those measurements wouldn't be implicated I don't think because the clamps aren't doing the work. Makes no sense because the width of the pic rail on the upper in question is slightly wider than the other rails

 

[mdmp5]

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motherfucker

 

[flyer]

I had a PRI extended rail riser with 30 MOA slope that would clamp on everything except the rail on an Aero Precision M5 upper.

I bought the upper as a Black Friday combo special and when I tried to get an RMA, no response from Aero.

Eventually I used a chainsaw sharpening file to deepen the cross bolt slots in the rail riser which allowed the clamp to tighten a bit more and then the riser fit.

Not the best ending to the story but at least it works and the part of the rail I had to file is on the bottom where you never see it unless you take off the riser.

So you're not the first.

 

[mgrs]

I had that problem with a badger 34mm unimount that would not clamp to any LaRue uppers when torqued. Two other badger mounts worked OK on the same upper and the first mount worked fine on everything else. Sometimes tolerances stack and you lose.

 

[mdmp5]

I understand tolerance stack, however, I’m no engineer, and when I took a few measurements, it is inconceivable why this is happening.

So if you guys have experienced it, I think I have my answer. Thank you