I. Scope Bases
Assuming you have selected a rifle scope to go with your rifle, you must securely attach it to your rifle. Scope bases and rings serve that purpose.
The bases attach to the rifle receiver to provide a foundation for the rings. The scope bases are also a sort of adapter that allow almost any scope to be mounted on almost any rifle.
The rings attach to the bases and hold the scope. The mounting system must secure the scope during transportation, handling, and, especially, during recoil.
Due to the popularity and availability of rifle scopes, modern rifles are designed to accept a variety of scopes.
The safety levers and bolt handles of modern bolt action rifles are positioned to be operated without interference from scopes.
Modern rifles, including lever action rifles, typically eject cases to the right instead of directly upward where the cases would strike the scope.
Twenty-two caliber rimfire rifles often have two parallel lengthwise grooves milled near the top of their receivers to attach scope rings directly to the receiver.
Some rifles even have scope bases as an integral part of the receiver.
And rifles that do not have integral scope bases are drilled and tapped for scope base screws at the factory. Such feature have made mounting a scope much easier.
Despite these design features, you still must select the correct combination of bases and rings that will accommodate the length of rifle scope, scope tube diameter, objective lens bell diameter, and eye relief.
In addition, the bases must also fit the make of rifle and its receiver length.
Luckily, an assortment of base lengths, ring sizes and heights, finishes, and styles is readily available to mount almost any scope on almost any modern rifle.
In fact, there may be several combinations of bases and rings that will work. You must decide which combination best meets your needs.
This article may help you sort through the options available to select the correct scope bases for your rifle. So keep reading.
Not sure which scope bases to order for your rifle? Well, you've come to the right place. Keep reading to learn how to select the correct scope bases to securely attach a scope to your rifle.
1. Integral Scope Bases
Your rifle may have integral scope bases or scope rails.
Models offered by Ruger®, Sako®, and BRNO CZ® have integral bases. Tikka® rifles have integral scope rails.
If so, you may choose to attach the ring mounts directly to the integral bases or mount additional bases on top of the integral bases.
(You can skip to the next article in this series, Selecting Scope Rings, if you decide to attach rings directly to the integral bases.)
If, in some rare case, you cannot find rings to fit integral bases, you may have to mount additional bases on top of the integral bases then select rings that will fit the new bases.
Unless your rifle's receiver has integral scope bases or rails or you will be mounting a scope on a .22 rimfire rifle with scope ring grooves, you must select the type of scope bases for your rifle.
2. Types of Scope Base
2.1 Attachable Scope Bases
Attachable scope bases get attached to the rifle receiver with screws.
There are many varieties of attachable scope bases available. Since they are all designed to maintain scope security during rifle handling and recoil, the type of bases to install is usually a matter of preference.
The two most common types of bases are the cross-slot rail type (also called the Weaver-style) and the rotating-dovetail type (often called the Redfield-style).
Both Weaver-style (cross-slot rail) and Redfield-style (rotating-dovetail) bases and rings are currently available from several manufacturers.
Quick-release bases are another type. There are a few other types, but the cross-slot rail, tactical, rotating-dovetail, and quick-release types are detailed in this article.
2.2 Cross-Slot Rail Scope Bases
Cross-slot (Weaver-style) scope bases are a type of attachable scope bases.
After the bases have been attached to the receiver, the scope rings, which are sold separate from the bases, are attached to the bases.
The front ring and rear rings both attach to the bases the same way.
New rings for cross-slot rail bases of the equal height are interchangeable between front and rear bases.
(New rings are interchangeable between front and rear bases but the bases themselves may not be interchangeable between front and rear positions on the receiver.)
The bottom halves of the scope rings are placed on top of the cross-slot rail base then clamped to the sides of the base. Lateral screws are tightened to secure the clamps to the rail.
2.3 Tactical Scope Bases
Also called "Picatinny" bases, tactical bases are heftier than standard scope bases. They resemble cross-slot bases with many more, evenly-spaced cross-slots.
Tactical bases, with their slightly wider (0.206" compared to 0.180") cross-slots, accept both tactical scope rings and standard weaver-style cross-slot rings.
However, standard cross-slot bases will not accept the thicker recoil tab and larger cross-bolts of purely tactical rings.
In addition to police and military riflemen, extreme long-range varmint hunters and competition shooters often install tactical scope bases on their rifles.
Besides being heftier than standard bases, the tactical bases with 10 or 20 MOA (minutes-of-angle) of forward cant provide some of the additional elevation required to shoot long range.
The built-in forward cant eliminates the need to install a shim beneath the rear scope base to sight-in at targets beyond 600 yards.
2.4 Rotating-Dovetail Scope Bases
The front and rear rings each attach to their respective bases differently in the rotating-dovetail type base.
A dovetail stud protrudes from the bottom of the lower half front ring. This stud fits into a recess in the front scope base. The stud locks the front ring into its final position when the ring is rotated 90 degrees.
On the other hand, the bottom of the rear ring is flat. It has no protruding stud. Instead, two laterally opposing windage screws in the rear base secure the rear ring. The lateral screws allow coarse external windage adjustments.
A variation of the rotating-dovetail type is the dual rotating-dovetail.
Dual dovetail bases and rings provide more security for scopes mounted on magnum rifles.
The front ring of the dual dovetail system attaches to its base the way described above for the single rotating-dovetail front ring.
However, the rear ring also attaches to the rear base the same way the front ring attaches to the front ring. There are no laterally opposing windage screws on the rear base. Hence, the rear ring of the dual rotating-dovetail system is not adjustable for windage.
(All the windage adjustments, as well as elevation adjustments, must be made with the scope's internal adjustments.)
The advantage of the dual rotating-dovetail system over the rotating-dovetail is its security.
There are no laterally opposing windage screws to work loose as with the single rotating-dovetail system.
(Like the new front and rear cross-slot rings, new rings for the dual rotating-dovetail system are also interchangeable between front and rear bases.)
2.5 Quick-Release Scope Bases
A quick-release mounting system is another option.
Detaching the scope and storing it separately may prevent damage to the scope. Quick-release mounts allow the scope rings to be easily separated and reattached to the bases.
The quick-release bases do not detach from the receiver; the rings, with the scope installed, detach from the bases.
Quality quick-release mounts allow the scope to be reattached with very little change in zero.
You may settle on a quick-release mounting system if you will be storing your rifle in a confined gun safe or will be transporting it commercially.
Also, a second scope installed within its own rings and previously zeroed could be a spare scope if the first scope has been damaged on a hunting trip.
Other reasons for choosing a quick-release mounting system include the ability to change scopes to match the hunting environment or to detach the scope to use the sights.
Or, since you normally hunt with only one rifle at a time, a single scope with quick-release rings could be switched between rifles with compatible bases.
Some quick-release systems require both special bases and special rings. Rotating two thumb levers on the left side of the base forward engage a stud protruding beneath each ring.
The rings are pulled down and secured solidly to the base. Rotating the thumb levers rearward releases the rings.
Other quick-release systems consist of quick-detach rings that attach to standard cross-slot bases. Instead of requiring a wrench or screwdriver, one thumb lever on each of the rings is used to tighten and loosen the ring clamps.
3. One-Piece or Two-Piece Scope Bases
Whether you decide to attach cross-slot rail, rotating-dovetail, or quick-release system, you must choose between a one-piece base design and a two-piece base.
Two-piece bases can be purchased as a set of two (one front and one rear base). A one-piece base is one long base that spans from the front of the receiver over the ejection port to the rear ring of the receiver.
Cross-slot rail, rotating-dovetail, and quick-release bases are available in both designs.
Some shooters claim the two-piece design makes it easier to load a bolt-action rifle through the ejection port because the ejection port remains unobstructed. Others believe the one-piece design provides additional stiffness to the receiver over the ejection port to support long, heavy barrels.
Whether you choose a one-piece design or a two-piece design may depend on the kind of shooting you will be doing.
Shooters who are concerned about receiver stiffness should purchase one-piece bases that attach to the receiver with four screws instead of the normal three screws (two at the front and only one at the back).
A one-piece / four-screw base should also be a consideration for rifles with heavy recoil. One-piece "tactical" bases are an example of bases that attach with four screws.
The front base of a two-piece system can be reoriented at its respective position to accommodate a scope with an unusually short main tube.
Normally you would orient both bases so the rings will attach as far forward as possible on their respective bases.
By reorienting the front base so its ring will attach toward the middle of the receiver you may be able to install a scope with a short tube.
One-piece cross-slot bases provide for installation of scopes with short tubes in a different way. One-piece cross-slot bases have multiple cross-slots at both front and rear positions.
Multiple cross-slots on a one-piece base allow rings to be attached at a variety of locations along the rail to accommodate a range of scope lengths.
Both rotating-dovetail and quick-release bases accommodate scopes with unusually short or unusually long main tubes in another way - they accept special rings called extension rings.
4. Scope Bases For Your Rifle
No matter which type of bases you choose or whether you choose a one-piece or two-piece base design, you must select bases that match your model of rifle.
Screw hole spacing is the obvious reason scope bases will not mount on any rifle. The screw holes in the bases must align with the screw holes in the receiver.
Another reason is mating surface contours.
Not all models of rifles have the same receiver top contour. Bases that match the top of one receiver will not precisely match the top of the receiver of a different model.
Some bases fit only one specific model of rifle offered by one manufacturer. Other bases may fit several models offered by a particular manufacturer.
Heck, certain bases may even fit several models of rifles offered by different manufacturers. Scope base manufacturers provide tables in their catalogs and on their websites to help you select the correct bases to match your rifle.
If you will order a one-piece base, be sure its length matches the length of your rifle's action.
Some bolt-action models are made in two different lengths: short-action (SA) for short and medium length cartridges and long-action (LA) for longer cartridges.
The screw holes of a one-piece base for a long-action will not align with the screw holes of an SA receiver.
Similarly, the screw holes of a one-piece base for a short-action will not align with the screw holes of an LA receiver.
If your rifle has a bolt-action, determine whether or not its model is made in two different lengths. If it is made in different lengths, determine whether yours is a short-action or a long-action (check the rifle owner's manual), then order the correct length of one-piece base.
Still not sure? Consider ordering a two-piece base. A two-piece base will fit either length bolt-action. Keep in mind, a one-piece base may not be available for every make and model of rifle.
5. Steel or Aluminum Bases
Some types of scope bases are made of steel. Rotating-dovetail bases, for instance, are always made of steel. Others types of bases are made of aluminum. A few brands and types are available in both steel and aluminum. Cross-slot and tactical bases are available in both.
You must decide between steel or aluminum if the brand and type of base you are interested in is available in both.
Steel or aluminum?
Are you more concerned about accuracy or light weight? Steel bases are more resistant to heavy recoil than aluminum bases. A one-piece, steel base will provide more rigidity to help the receiver support a long, heavy, free-floating barrel than an aluminum base.
All other factors being equal, steel provides more accuracy than aluminum. But steel bases are more expensive than aluminum bases. And they are heavier. A one-piece steel base is much heavier than a two-piece aluminum base.
Order steel bases if you are more concern about accuracy or if your rifle is chambered for a magnum rifle cartridge. Order aluminum bases if you are more concerned about the carrying weight of your rifle.
One final decision to make concerning bases is the finish.
Scope bases are commonly available with matte black (dull black), gloss black (shiny black), or silver finishes (bare metal).
If the finishes of the scope and rifle's receiver are the same, you will probably select bases and rings of the same finish.
If the finishes of your scope and rifle's receiver are different, you will probably want bases with the finish that matches the receiver (and rings that match the scope).
A finish that matches the receiver gives the appearance that the bases are a part of the receiver (and rings that match the scope give the appearance that the rings are a part of the scope).
Or you could choose bases and rings with contrasting finishes.
Hey, it's your choice.
So, those are some of the considerations in choosing scope bases and some of the options available. You'll choose a base style such as cross-slot rail, rotating-dovetail, quick detach, or other; one-piece or two-piece base; bases to match the receiver contours and length; and a finish that matches (or contrasts) the receiver.
II. Scope Rings
A scope mounting system consists of two scope rings and one or two scope bases.
Scope bases, as described in the previous section, provide a foundation for the scope rings. Scope rings attach the rifle scope to the bases. The rings must mate to the top of the bases, fit the scope, and be the optimum height.
Choosing the correct scope rings can be challenging. Selecting the wrong rings is inconvenient; even frustrating. This article has been provided to help you order the correct scope rings - hopefully on the first attempt.
Scope rings are sold separately from scope bases. They are normally sold as a set of two.
You will only have to order one set for each scope.
You will receive two identical rings if you order a new set of cross-slot (Weaver-type), dual rotating-dovetail, or quick-release scope rings.
If you order a set of single rotating-dovetail (Redfield-type) rings, you will get one front ring and one rear ring.
Scope Ring Diameter
Whether you order ringmounts for integral scope bases or rings for attachable bases, you must order rings of the correct size to match the diameter of the scope tube.
Ring are either 3/4-inch, one-inch, 30mm, or 34mm diameter to accommodate either 3/4-inch, one-inch, 30mm, or 34mm diameter scope tubes, respectively.
One-inch and 30mm are currently the most common scope tube diameters.
The diameter of the scope rings you order must match the scope tube diameter of the scope you intend to mount.
Three fourths-inch diameter rings of any brand will fit a three-fourths inch diameter scope tube of any brand.
Likewise, one-inch diameter rings of any brand will fit a one-inch diameter scope tube of all brands.
And, that's right; 30mm diameter rings of all brands will fit a 30mm diameter scope of any brand.
However, a one-inch diameter scope tube will be loose in 30mm rings. And, obviously, a 30mm diameter scope tube would not fit into one-inch diameter rings. (One inch is 25.4mm and 30mm is about 1+3/16 inches.)
Do not confuse the scope objective lens diameter with the scope main tube diameter. Both are listed with the scope specifications and both may be measured in millimeters. But only the scope main tube is enclosed within the scope rings.
Scope Ring Height
Selecting correct ring height is the most difficult decision to make when ordering scope rings.
Rifle scopes should normally be mounted as low as practical to the rifle receiver. However, the scope on a bolt action rifle must be mounted high enough to allow the bolt handle to be cycled.
(Clearing the bolt handle normally will not be a problem with a modern bolt action rifle because modern bolt handles are configured to be operated even with low mounted scopes.)
Also, the objective lens bell, with its lens cap installed, must clear the top of the barrel by at least 1/8-inch.
The larger the objective lens, the higher the scope must be mounted. More than 3/8-inch scope clearance above the barrel is too much with most rifles.
The length of the scope ring stem determines ring height.
Scope ring manufacturers offer rings of different heights to accommodate various scope objective lens bell diameters. Most brands are available in low, medium, and high. Some brands are even offered in extra low or extra high.
However, the choices of scope height are a bit confusing because there is no standard method to measure ring height.
Some ring manufacturers specify scope height measured from the bottom of the stem where it will contact the base to the bottom of the ring saddle.
Other manufacturers measure ring height from the bottom of the stem to where the rings split horizontally.
So the scope rings designated as "high" from some manufacturers may actually mount a scope lower than "medium" scope rings from other manufacturers.
But do not only consider scope ring stem length when choosing scope rings.
The thickness of the base, the diameter of the scope main tube, and the taper of the rifle barrel also contribute to scope mounting height.
Ring To Base Fit
Rings for cross-slot rail bases are not interchangeable with rings for rotating-dovetail bases.
That is, cross-slot rings will fit only cross-slot bases while rotating-dovetail rings will fit only rotating-dovetail bases.
So if you ordered cross-slot bases you must order cross-slot rings to match.
If you chose rotating-dovetail bases you must choose rotating-dovetail rings to match. And dual rotating-dovetail rings will fit only dual dovetail bases.
Obviously, the capacity of rings is different between one-inch and 30mm diameter rings. However, both 1-inch and 30mm rings will attach to the same bases.
Therefore, one-inch and 30mm cross-slot rail rings will all attach to the same cross-slot rail bases. And both one-inch and 30mm rotating-dovetail rings will attach to the same rotating-dovetail bases - at least if the rings and bases are from the same manufacturer.
Cross-slot rings of one brand will probably fit cross-slot bases of any brand. Similarly, rotating-dovetail rings from of one brand will probably fit rotating-dovetail bases of any brand.
However, to ensure a reliable fit, the bases and rings you order should be the same brand.
That does not mean the combination of bases and rings you order has to be the same brand as the scope itself.
Provided the brand A ring diameter is the same as brand B scope tube diameter, brand A bases and rings will fit a brand B scope. Besides, not all scope manufacturers make scope mounts anyway.
See-Through Scope Mounts
You may consider see-through scope mounts if you anticipate using sights for close shots and using the scope for farther shots.
See-through rings have circular stems that allow a clear view of the sights beneath the scope.
However, see-through rings require the scope to be mounted higher than normal to allow a clear view of the sights.
You may not be able to get solid cheek contact with the stock for consistent eye alignment with the scope mounted so high.
Some styles of see-through rings require cross-slot bases. Others attach directly to the receiver with screws. See-through rings for .22 rimfire rifles grip the scope mount grooves in the receiver.
Quick-Release Scope Rings
Quick-release rings allow the rings, with the scope installed, to be easily detach and reattach to the bases.
Quick-release rings are handy to remove the scope for storing your rifle in a confined gun safe or to prevent scope damage during transportation or maintenance.
You should also consider quick-release rings if you plan to switch one scope between multiple rifles frequently.
Each of the rifles must have bases that match type of rings installed on the scope.
Conversely, several scopes could be exchanged on one rifle like when you carry a spare previously zeroed scope just in case the installed scope is damaged on a remote hunting trip.
In this case, each of the scopes must have its own set of rings compatible with the bases installed on the rifle.
There are two types of quick-release systems. With quick-detach rings, the quick-release system is part of the rings. These quick-detach rings fit standard cross-slot bases.
No special bases are required.
One-half turn of the release lever on each ring loosens its clamp for easy removal from its base.
One-half turn of the levers re-tightens the clamps to their bases. The rifle zero must be verified before hunting with this type.
The quick-release levers of the Leupold® QR™ mounting system are part of special bases instead of the rings.
The thumb levers are located on the left side of the bases instead of on the rings.
These quick quick-release bases will only accept special rings. Rotating the thumb levers forward draws the rings down securely to the bases.
Turning the thumb levers rearward releases the rings from the base. Leupold ensures its quick-release system will return the scope to its zero position when reinstalled.
The ammunition and time saved from not needing to re-zero should compensate for the higher price.
Tactical Scope Rings
Many competition riflemen prefer tactical rings to secure scopes to their rifles.
Tactical rings (sometimes called Picatinny rings) are a bit heftier than standard scope rings and the jaws clamp the base over a wider area.
Tactical scope rings provide a larger contact surface around the scope tube.
The halves of the rings are secured with either four or six screws instead of the normal two screws.
The extra security provided by tactical rings helps to prevent the scope from being knocked off zero.
But tactical scope rings on a hunting rifle?
Why not? Tactical rings will handle recoil from magnum cartridges better than standard rings.
Sure, tactical rings may not be as sleek as standard scope rings. But the extra security provided by tactical rings is desirable on hunting rifles as well as competition rifles - perhaps more desirable.
Competition shooters are more careful with their prized rifles in a shooting range environment than most hunters are with their rifles in hunting environments.
Both standard cross-slot (Weaver-type) rings and tactical rings will fit tactical bases.
However, tactical rings, with a larger cross-screw or thicker recoil tab (0.205"), will not fit the narrower (0.180") cross-slots of standard cross-slot (Weaver-type) bases.
Therefore, you can order either tactical rings or standard Weaver-type (cross-slot) rings if you order tactical bases.
On the contrary, if you order a standard cross-slot base, you must order standard cross-slot rings to fit or you must order tactical-style rings with narrower cross-screws to fit the slots of standard cross-slot bases.
The specifications of tactical rings that will fit standard cross-slot bases usually state those rings will fit Weaver-type bases.
Extension Scope Rings
Perhaps you have realized by now that low power scopes - scopes used by big game and dangerous game hunters - have relatively short main tubes.
Often these scopes are mounted on rifles that shoot magnum cartridges. Rifles that shoot magnum cartridges have long receivers to allow the bolt enough travel to feed magnum length cartridges from the magazine.
Trying to mount a short scope on such a long receiver could pose a problem.
If the scope tube barely spans the distance between the rings, there may not be enough leeway to slide your scope forward or backward to adjust for eye relief.
Short scopes can be mounted on two-piece cross-slot bases by orienting the bases on the receiver so cross-slots and, therefore, the rings will be closer to the middle of the receiver.
However, a one-piece cross-slot base cannot be reoriented. It can be attached to the receiver in only one direction.
However, one-piece cross-slot bases have several cross-slots to attach the rings at various positions along the length of the base. The rings can be attached at whichever cross-slot positions provide the best eye relief.
Rotating-dovetail bases and Leupold® QR Mounts™ accommodate short scopes a different way.
The front base will accept an extension ring to shorten (or lengthen) the span between the rings. The front ring is offset about 5/8-inch longitudinally from the stud that fits the base.
Extension rings can be used to reduce the space between the rings 5/8-inch to accept extremely short scopes or turned around to expand the space 5/8-inch to accept long scopes.
If your rifle has integral bases and you decide to use those bases without installing additional bases, you must attach rings mounts to the integral bases.
Ringmounts are scope rings that attach directly to integral scope bases or rails.
The integral bases on a Ruger® 77 rifle accept ringmounts designed for the Ruger® 77 rifles.
The integral bases on a Ruger®#1 rifle accept ringmounts designed for the Ruger®#1 rifles.
Ringmounts designated for CZ receivers will fit only BRNO CZ® integral bases.
And ringmounts designed for Sako® rifle receivers will fit Sako® integral bases.
Neither cross-slot rings nor rotating-dovetail rings will fit integral bases.
If, in some rare case, you cannot find ringmounts to fit integral bases or if you prefer to have attachable bases on your rifle, you can mount separate bases on top of the integral bases then select rings that will fit the new bases.
Integral bases are often drilled and tapped by the manufacturer to accept additional bases for this reason. Other types of attachable bases clamp onto the integral bases.
Twenty-two caliber rimfire rifle receivers usually have two parallel scope mounting grooves. You could use ringmounts specifically designed for .22 rimfire rifles to mount a scope.
Neither cross-slot nor rotating-dovetail rings will work there.
The space between the parallel grooves on the receiver is either 3/8-inch or 11mm. Select rings with a 3/8-inch wide clamp or 11mm wide clamp to match.
Some brands of .22 rimfire ringmounts will fit both 3/8-inch and 11mm spaced grooves on .22 rimfire rifles by turning the moveable clamp jaw over.
If your rifle does not have integral scope bases, you must order scope rings to fit the attachable bases you have selected.
Steel or Aluminum
Just like scope bases, scope rings are made of either steel or aluminum. Some brands and models of scope rings are available in both. Others are available in one or the other.
Should you order steel or aluminum rings? Normally, the material of the rings should be the same as the bases. Order steel rings for steel bases or aluminum rings for aluminum bases.
However, you could order aluminum rings for steel bases if suitable steel rings are not available. Aluminum cross-slot rings have steel cross-screws and steel moveable jaws anyway.
Attaching steel rings to aluminum bases is not recommended. All scope bases must resist the inertia of the scope and its rings during recoil. Steel rings, being heavier than aluminum rings, have more inertia that the bases must resist. This additional inertia may cause hard steel ring jaws to wear into softer aluminum bases during heavy recoil causing the rings to loosen.
The final decision for selecting scope rings is probably the easiest - choosing the surface finish of the scope rings.
Most scope ring brands are offered in gloss (shiny) black, matte (dull) black, or silver finish.
Most customers order the scope ring finish that matches their scope. This makes the scope and rings appear to be one unit.
Some like the rings to contrast with the scope finish. There is nothing wrong with ordering a set of rings that will contrast with the scope finish, unless you are a hunter.
Most hunters order matte black rings for a matte black scope to reduce game-frightening glare.
Since scope rings attach the scope to the bases, they must be compatible with the both the scope bases and the scope.
The rings must mate to the bases. Also, be sure to order scope rings that have the capacity to accommodate the main tube diameter of your scope and the height to allow the objective lens bell (with lens cap installed) to clear the top of the gun barrel by just a bit more than 1/8-inch.
The scope ring finish is usually a matter of preference.