upper troubles

[cz7]

two different uppers ,both have the key hole marking both fit a rra lower set up but one will fit the Reich racing lower ...so what the hell ???

[lunchbox]

Where does it hit? RRA are notorious for tight lowers, if it fit RRA lower then other might be out of spec. Just the first thing that popped out at me...

[mtdawg169]

two different uppers ,both have the key hole marking both fit a rra lower set up but one will fit the Reich racing lower ...so what the hell ???

Who the heck is Reich Racing?

You need to take a few measurements. Measure the takedown & pivot lugs on the uppers and the width between the matching locations on the lowers.

[AKDoug]

Keyhole means nothing other than the raw forging came from Cerro Forge. Manufacturers buy the raw forgings from various vendors and finish machine them to their specs.

[AlphaKoncepts]

Keyhole means nothing other than the raw forging came from Cerro Forge. Manufacturers buy the raw forgings from various vendors and finish machine them to their specs. This is your answer, the keyhole marking is nearly meaningless to the size and fit and finish of the receiver.

I'll give you an idea of quality control. Two lowers from one manufacturer. One absolutely would not fit the Noveske Ambi safety, the other marked in the very next serial number, assumingly manufactured at the same time by the same people in the same factories, fit in with no problem.

Something is out of spec or may be within spec, and tolerances are stacking. What exactly is preventing the fit? I assume the front pivot pin fits snug but the rear take down pin won't penetrate through the receivers, or something else?

[cz7]

4 different lowers and 3 different uppers ,where swapped around ...and the most damning thing was found not one was close to one set of specs ...like the take down hole[center] of the upper to base of the center .250 is spec to diagram found on the web ...you mix them up some will wiggle ,others will not close ,and another very tight lock up rra,colt,mega s/w lowers uppers rra mega s/w....cant we have a set specs for all to be the same .......