Scope mount basics - part one
by B.B. Pelletier
A lot of airguns are scoped these days, so I thought it would be nice to cover some of the basics about scope mounts and rings. With airguns, more often than with firearms, scope mounts and rings come together as one unit. While firearms have separate bases called mounts that attach to the rings, most airguns have their bases installed on the guns, so the rings are made to fit to these guns.
Get this handy scope-mounting catalog direct from B-Square.
B-Square set a high standard for airgun mounts!
The most common scope-mounting base found on an airgun is an 11mm dovetail, but you need to know that gun manufacturers have not always adhered to that dimension as close as they should. B-Square publishes a free brochure about mounting scopes on airguns, and they have a chart that shows airgun mount bases range between 10.6mm and 14.1mm, so you can expect some deviation from gun to gun. Get this free brochure by calling B-Square at 800-433-2909, 8am-5pm (Central time), Mon-Fri. Ask for customer service.
Scope rings with built-in mounts have to span a wide range of sizes to clamp to a gun. Once again, B-Square is the leader is designing mounts that fit a wider range of airguns, plus they make special-purpose dedicated mounts for guns that vary by too much, like BSA.
Stopping scope ring slippage
If your gun recoils, you need a scope stop. NO AMOUNT of clamping pressure alone can hold a scope mount on a recoiling airgun. There must be a positive stop to arrest rearward motion, or the mount will back right off the gun. Some rifles such as the Webley Tomahawk have only the rear runout of their dovetails for this function. It's not the best way to do things, but the Tomahawk doesn't kick enough to make it a problem. Just be sure to back the rear mount (when using two-piece rings) or the rear of the one-piece mount completely to the end of the dovetail cuts so they can grab the mount when it tries to back up.
Most guns have holes or notches to arrest the mounts during recoil. The scope stop pin goes either into the appropriate vertical hole or the cross slot on the receiver. The stop pin can be part of the rings or a separate item. B-Square makes a special scope stop for the Webley Patriot because its stop notches are quite different than those found on most rifles.
Weaver and Picatinny mounts won't work for airguns
Neither of these fine mount-locking systems work on airguns as they come from the factory. B-Square makes an 11mm to Weaver adapter that turns a simple 11mm dovetail into a Weaver base. If you already have Weaver rings, you need this adapter.
There's more to talk about, but that's a good start. I'll get back to scope mounts and rings very soon!