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The bases and rings used to connect a riflescope to a firearm are often the weakest link in a shooting system. Without a properly fitted connection, the very best scope and rifle combination is rendered useless. Often it is impossible to tell if you have an unsecure or ill-fitting connection until you're at the shooting bench or in the hunting field, where a poor mount or installation may show itself as inconsistent at best, and at worst cause an excess expenditure of valuable time and ammunition or a wounded animal. Think of scope mounts as the lug nuts of the shooting world.
Once installed you should never have to trouble over a loose wheel. Choosing rings and bases is not the time to pinch pennies or just make due with "good enough." The money spent will be more than made up for in reliability, ruggedness, and peace of mind. Glossary: These terms are thrown around everywhere quite loosely. Take them with a grain of salt.
Picatinny/1913
Picatinny/1913 rings and bases are similar to Weaver style. The main difference is that they are based on specifications standardized by the U.S. Picatinny Arsenal in 1913. The main physical difference is in the size of the recoil lugs on the bottom of the rings and the corresponding larger size of the recoil slot in the top of the base. This size is .206", much bigger than the .180" in the Weaver style. Therefore, a Picatinny ring will not fit into a Weaver base, but a Weaver ring will fit into a Picatinny base. Some manufactures label their products as Picatinny/Weaver but are actually Weaver style. Some Picatinny rings are tightened with an inch-pound torque wrench to ensure a return to zero when reinstalled. Our military M-4 carbines utilize Picatinny rails.
Leupold Style
The Leupold style of bases (also Redfield, Burris, and others) are a standard that non-Weaver style mounting systems are measured by. They can be one or two pieces, and are steel, sleek, and strong. They are reliable and trouble-free. There is almost as much interchangeability between manufacturers with the Leupold style as there is with Weaver style systems. Unlike Weaver style rings, the Leupold system is not easily detachable. The top half of the rings must be separated to remove your scope. The front ring is kind of a press fit, with a protruding, beveled rectangle of metal under the ring, turned tightly into a corresponding dovetail slot in the front base. Normally, the two halves of the rings are loosely assembled, and a scope ring tool or a one inch wooden dowel or a screwdriver handle is inserted between the pieces to gain leverage to turn the ring into the base. This is a press fit and cannot be done by hand.
The rear ring sits flush atop the base and is held there by two opposing screws tightened into it. The screws have a leading edge that fits into corresponding slots in the ring. The base screws are tightened into each other, squeezing the ring between them tightly and immovably. By backing out one screw and tightening the other, the ring moves laterally on the base, effectively acting as a windage adjustment. This is of minimal importance unless your base holes are drilled off-center, or there is some other problem that makes your gun shoot left or right so much that it can't be easily corrected with minor internal scope adjustments.
Rifle Scope Rings
Circular clamps used to hold a riflescope and connect it to a previously installed base on a gun. The ring inside diameter must match the scope's outside diameter. These are mostly one inch or 30mm. The height of the ring must be chosen in regards to the objective lens outside diameter, the ocular bell size, scope length, eye relief, bolt lift, and barrel contour.
Weaver Style Rings
Everyone makes a version. Some are aluminum, some are steel, many are a combination of both. They are made to clamp onto a 7/8" wide base. There is a metal bar or connection screw underneath these rings called a recoil lug that fits the corresponding .180 wide recoil slots on Weaver style bases. Recoil lugs under rings prevent fore and aft movement of the scope during recoil and handling. Most Weaver style rings are detachable from their bases with the scope still in them, and can be reinstalled without major loss of zero. Swapping scopes for different purposes is also facilitated.
Extension Rings
Rings of any style with a cantilever portion that allows for a shorter mounting distance between rings. Extension rings are useful to mount short scopes on long receiver rifles or to manipulate eye relief slightly. Normally extension rings offer another 1/2" of mounting leeway.
Tipoff Rings, .22 Rings and 3/8" Dovetail Rings
3/8" dovetail rings are normally used on grooved receivers. Grooved receivers have cuts running lengthwise in the top of the gun deep enough for the claws of the rings to firmly grip onto. Grooved receivers are normally found on .22 rifles and airguns (although some European .22s and air rifles have grooves that are 11mm or 13mm). Sometimes there is actually a 3/8" base screwed into the receiver instead of grooves cut into it, often because of lack of metal thickness of the receiver. These 3/8" rings may have a circular diameter to hold a scope with a main tube of 30mm, 1", 7/8" 3/4" or others. A standard .22 ring may be called a "one inch tip off", a "one inch .22 ring", or a "one inch 3/8" dovetail ring". Some grooved receiver .22s are drilled and tapped for Weaver style bases. It is prudent to use these much larger bases if available. Weaver style bases simply offer more area for the rings to grab onto.
Quick Detachable/Quick Release Rings
Quick Detachable or Quick Release Ring systems incorporate some kind of lever to quickly and easily remove your scope for transport, cleaning, exchanging scopes, or other reasons. Some are Weaver style, some are proprietary and require matching bases. A perfect return to zero is normally not accomplished when reinstalled.
Ring Height
Scopes should be mounted as low as comfortably possible without touching the barrel. A slightly higher ring may be used to provide clearance for scope caps.
50mm scopes will generally use high rings. Heavy barrels may require extra-high. Mediums may occasionally work with standard contour barrels.
42-45mm scopes will mostly use medium rings with standard contour barrels.
40mm scopes will generally use low rings with standard contour barrels.
Flattop rifles will need super-high rings with an optical center of 1.5 inches or just slightly less for a proper cheek weld.
Rifle Scope Bases
A simple steel or aluminum platform in one or two pieces that connects to a firearm receiver via clamps or screws and accepts scope rings into them or onto them secured by clamps, screws, or friction secured dovetails. Some receivers have bases built into them, notably many Ruger/Sako rifles, target and hunting handguns, and various military long guns like the M-4 type.
Weaver Style Bases
Basic aluminum rails to fit the contour of the firearm receiver. Probably the most commonly used type for sporting firearms. These are inexpensive, and readily available for most guns. Sometimes found manufactured in steel. These are 7/8" wide and vary slightly from manufacturer to manufacturer. The slots running crossways are called recoil slots, and on Weaver style bases will measure around .180" wide.
Dual Dovetails
Dual dovetail bases are the same as the standard Leupold style, but instead of the windage screws holding the rear ring to the base, they are omitted, and the rear ring is turned in, just like the front. This system does not offer the extra windage adjustments that the standard bases offer, but it is normally not of major importance, and you may prefer the cleaner lines and fewer parts that the dual dovetail system offers.
Rifle Scope Mounts
Mounts generally are a ring and base combination in one piece. See through mounts are common, as well as saddle mounts for shotguns. Mounts from companies like B-Square, NcSTAR, and DedNutz normally do not require gunsmithing to install, and are easily removed without harm. Older handguns and longguns may utilize these mounts, making the gun a much more useful and fun firearm that can be shot more accurately.
STANAG
STANAG means "standard agreement" and is a standardized mounting system used by NATO forces. This system is not widely used in the U.S. STANAG rings and bases must be used together, although there are some STANAG mounts that incorporate a Picatinny style rail that will accept Weaver/Picatinny rings as well as STANAG rings. STANAG rings will not install on standard Picatinny bases.
