This says Picatinny rail slots are 0.206" while Weaver rail slots are 0.180"
http://www.brownells.com/.aspx/lid=1...he_Difference_
I just took 4 ATI Mosin Nagant rails of a wide range of ages and they are between 0.152" and 0.159" wide in the slots.
I just pulled out (4) pairs of 30mm tactical rings from various source and tried to make them fit on the ATI rails and measured the cross bar:
0.185" does not fit
0.184" does not fit
0.187" does not fit
0.136" does fit [Weaver 48335 tactical]
I pulled out (4) pairs of 1" rings that are not tactical from various sources and tried to make them fit and measured the cross bar:
0.133" does fit
0.131" does fit
0.137" does fit [Burris Z ring needed bolt removed and ring slid on from the end of the rail]
0.126" does fit