Wondering what scope ring to purchase? We’ll help clarify the different rails mounts found on rifle receivers and explain the differences between the 11mm, 22mm, Weaver style and Picatinny rails.
11mm rails are found on many airguns as well as some rimfire rifles. 11mm rails are generally a small triangular cut (known as a dovetail) that is made directly into each side along the receiver. The inherent issue with the design is that the diameter of the receiver is not consistent among rifle manufacturers. Large diameter receivers may not leave enough material for a proper 11mm spacing while small diameter receivers may leave to much material in between the the cuts. In either case, 11mm may become 12mm or 10mm as required to leave enough material for strength. Some scope ring manufactures help overcome these subtle difference by giving the user the option to flip the scope ring clamp upside down for a better fit. If your 11mm ring doesn’t appear to fit the dovetail on your receiver very well, you may want to try another brand of ring or find one that is adaptable. To cope with recoil and prevent the rifle scope from moving, rifles with 11mm rails may have a small hole drilled in the center of the receiver while one of the scope rings will have a small pin or screw that projects out the bottom of the ring, other wise known as a recoil pin. Aligning the pin with the hole will help prevent scope ring movement under recoil but it does limit the user as to where they can place the ring alongside the receiver.
Weaver style rings, named for the first manufacturer of this style, utilize a separate rail attached to the top of the receiver. This rail can be attached by fasteners or machined directly into the receiver given that the receiver was manufactured with additional material on top. The Weaver rail, or also commonly referred to now as 22mm rail will have slots cut across the rail toward the front and the rear of the rail. Scope rings manufactured for the 22mm rail will have a cross bolt, generally 9/32” in width, that lies within these slots to prevent movement of the ring during recoil. As with the 11mm rail, scope ring placement is limited to where the cross slots are put into the rail although some manufacturers are adding additional slots in the rail for additional options for scope ring placement.
Picatinny rails are most commonly used by the military and more recently are becoming commonplace in the civilian marketplace. The size of the dovetails are so similar to the 22mm style that the rings are almost inter-changeable. The key difference is in the slots cut into the rail to prevent recoil. Picatinny slots are wider allowing for a stronger thicker crossbolt. Therefore the smaller crossbolt of the Weaver / 22mm ring will fit into the slot of a Picatinny rail, the larger crossbolt of a Picatinny scope ring will not fit into the slot of a Weaver rail. Picatinny rails also have slots cut the entire length of the rail exactly .394” apart allowing for matching multi cross bolt Picatinny scope rings to be attached.