Throwback Thursday—Scope Mounts

By CTD Blogger published on in How To

Sometimes it seems there is nothing more confusing to a new gun owner, and even some old hats, as installing a riflescope on a firearm. The sheer number of choices and options in optics alone are enough to write books about, and the ways to put the scope on the gun are even more complicated.

This article will attempt to clarify choices and make the novice gun owner’s job in choosing a way to mount a scope easier, while at the same time illuminate the myriad of options for any gun owner.

What You Need to Know (or Find Out)

When you start looking to mount a particular scope on your firearm, you need to know certain things before you start shopping for mounting options. To begin with, you will need to know your scope’s objective diameter, usually the last and largest number in the scope’s specifications. The objective diameter’s size determines the clearance needed for your scope. The next important measurement you need is the scope tube, determining what ring diameter fits your scope, usually 1-inch or 30mm.

You need to know what mounting system your rifle is equipped with—receiver grooves, Picatinny rail, Weaver dovetail base or nothing at all. The type of firearm you have and in some cases, what barrel type and contour, also affects what mounting system you need to use. A flat top AR-15 has vastly different ring requirements than a Remington 700 with a tapered barrel.

The Basics

The most common setup inquired about for putting optics on a long gun is mounting a traditional magnified riflescope to a traditional bolt-action rifle. Let us use this setup to explore the basics of putting a scope on a rifle. Traditionally, the scope attaches to the rifle by rings, that clamp around the scope’s body. In turn, the rings attach to a base, that normally attaches to the rifle’s receiver or action.

To add to the confusion, there are many variations of all of these components. There are ways to mount a scope that combine some or even all of these individual components. For example, mounting an EoTech HWS to an AR-15 rifle, where the scope has an integral mount that does not require rings, and the rifle has an integral rail that does not require a base.

Bases

The base is the part of the system that allows the scope rings to attach to the rifle itself. Traditionally bases attach to the receiver of a firearm by some sort of screw or bolt. Some rifles have built-in bases that are integral to the firearm.

Usually specific to a particular make and model of firearm, bases are also mostly exclusive to the type of rings they use as well.

Rings

The rings you select must be the same inner diameter as your scope’s tube diameter. The rings clamp onto the scope’s main tube, so the sizes must match. Most scopes are 1 inch diameter as are most rings. However, there are many 30mm scopes and rings, as well as a smattering of other choices, such as 34mm. The other end of the ring attaches to the rifle’s base, so it too must be compatible with your rifle’s particular base.

The important thing to remember is to match the rings with the scope and the base.

Ring Height

Ring height is one of the most confusing options for new gun owners. Scope rings come in differing heights to vary the distance from the scope’s centerline to the firearm’s base or receiver. The different ring heights allow you to mount scopes with different objective sizes in the proper place for a quick and proper cheek weld. Rings normally come in low, medium and high heights. There are extra low and extra high variations from some manufactures.

You should mount your scope as low as possible without the front of it—the objective bell housing—touching the barrel. The bolt handle must also clear the ocular bell or eyepiece at the back of the scope. The thing most often ignored when choosing scope ring height is the need for the scope’s height to match the shooter. When shouldering the rifle quickly, the scope should be at the correct height to look through it, without any additional up or down movement to get a good view through the scope.

Remember there is no perfect ring height to suit every person, as each person’s physiology is a slightly different.


In this illustration from UTG, Ring height is measured with “C”

Ring Height According to Leupold

  • 50mm objectives typically use HIGH rings. In certain instances, such as with extremely heavy barrels or some firearm models, EXTRA HIGH rings may be necessary.
  • 42-45mm objectives typically use MEDIUM rings. In certain instances, 45mm scopes may require HIGH rings.
  • 40mm objectives typically have enough clearance with LOW rings, though MEDIUM rings will give slightly more clearance, particularly when using a barrel with a thicker shank portion or heavier contour.
  • 28-36mm objectives typically use LOW rings. Again, in certain instances of a heavy barrel or heavy shank portion of a custom barrel, MEDUIM rings may be necessary; however, LOW rings will usually suffice.
  • 20-24mm objectives typically use LOW rings, but in some cases may also use EXTRA LOW rings. In this instance, bolt handle clearance of the eyepiece will come into play moreso than objective and barrel clearance, so consider it carefully.

No Leupold riflescope will fit into EXTRA LOW rings if using a one-piece base.

Ring Height According to Weaver

  • Use low 1-inch rings for up to 38mm scope objectives
  • Use medium 1-inch rings for up to 40mm scope objectives
  • Use high 1-inch rings for up to 44mm scope objectives
  • Use extra high 1-inch rings for up to 50mm scope objectives
  • Use 30mm low rings for up to 33mm scope objectives
  • Use 30mm high rings for up to 44mm scope objectives

For mounting a scope on a Harrington and Richardson Handi-Rifle or the NEF Pardner you will need at least medium and perhaps high rings clearance between the scope’s eyepiece and the rifle’s hammer. Now that we have discussed ring height standards, there are some notable exceptions—for the AR-15 and M4 series of rifles with flat top upper receivers, extra-high rings are the rule of thumb, but some applications use high rings.

Mounting Systems

Weaver

Black, Weaver-style rail for the Remington 700 rifle.

Weaver-style mounting systems have flat dovetail rails with slots.

The most common scope mounting system is the Weaver system. Found on many firearms from shotguns to semiautomatic handguards, the Weaver system utilizes flat dovetail rails with crosswise slots. The Weaver-style bases are 7/8 inch wide and designed to accept Weaver-style rings. Most ring manufacturers make a Weaver-style ring and or rail. On Weaver-style rings, the securing bolt for the ring runs underneath the web of the ring and fits into a corresponding crosswise slot in the Weaver base. This prevents any scope movement fore and aft under recoil. You can find the bases in one or two-piece configurations and made of steel or aluminum. The Weaver-style system allows the Weaver rings to be detached from the base with the riflescope still in the rings and reattached without any major loss of zero. The optic can be removed from the gun for maintenance, transportation or storage. The weaver system also allows for using different optics on one weapon or one optic on different weapons.

Picatinny and MIL-STD-1913

Picatinny rails are very similar to Weaver rails. The physical difference between Weaver and Picatinny rails are the width of the cut crosswise slots in the base and the spacing of these slots. The slots in Picatinny bases are wider than slots in Weaver bases. The spacing of these slots in a Picatinny rail is consistent and standardized. The Weaver style rail’s spacing of the cross slots are not standardized and the spacing is left up to the manufacturer. The recoil lugs on Picatinny rings are thicker to fit in the corresponding, wider, slots in Picatinny bases. Weaver rings will fit on Picatinny bases, but Picatinny rings will not fit on Weaver bases.

22 Rimfire Rings, Tip-Off Rings and 3/8-Inch Dovetail Rings

Most .22 rimfire rifles and airguns produced today have cuts running lengthwise in the top of the receiver for mounting rings. Some European .22s and air rifles have grooves that measure 11mm or 13mm. 3/8-inchdovetail rings clamp into the groove of the grooved receivers. These rings are also referred to as rimfire rings, .22 rings, and Weaver brands them as Tip-Off rings. There are also rifles found with 3/8-inch bases attached to the receiver with screws, and you can buy 3/8-inch bases to add to most firearms without them. Some rifles with a grooved receiver are drilled and tapped for Weaver style bases. We suggest using a Weaver-style base in these cases as they offer more area for the rings to grab and are more secure and stable.

Redfield Style

The second most common mount type is the Redfield style. This type of mounting system, like the Weaver, has many base and ring clones and manufacturers. Known for their sleekness and strength, the bases are one or two pieces. Unlike Weaver-style rings, Redfield-style rings are not detachable from the rail system.

You must separate the top half from the bottom half of the rings to remove the riflescope. The front ring in the Redfield system has a dovetail that turns into a corresponding slot in the front base, allowing the scope to pivot around this point. Held by two opposing windage screws tightened into the ring, the rear ring in the Redfield system sits on the base. The windage screws have a leading edge that fit a corresponding slot in the ring. By loosening one screw and tightening the other, the ring moves right and left on the base, acting as an external adjustment. This adjustment allows you to zero the windage of your scope without using its internal adjustments.

Dual Dovetail (DD) Systems

Dual dovetail bases are the same as Redfield style, however, instead of the windage screws holding the rear ring to the base, the rear ring turns in just like the front. This system does not offer the windage adjustments that the standard Redfield style bases offer. This system is secure and very strong for heavy recoiling rifles and handguns.

Clamp-on Mounts

For guns not drilled and tapped for scope mounts, B-Square, S&K, ATI and other manufacturers make clamp-on mounts allowing easy scope mounting. Easy to remove without modifications to the firearm, these mounts typically do not require gunsmithing. Older and military surplus firearms often benefit greatly with these style mounts.

Which of the mounting systems listed do you prefer or do you like the new KeyMod or M-LOK systems better? Tell us which one is your favorite and why in the comment section.

This article originally posted in May, 2010.

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Comments (14)

  • GDean

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    I see that Cheaper Than Dirt carries the 1″ version of the mount I’ve suggested, and a an excellent price also. Don’t know if they offer the 30mm version.

    Umarex USA RWS Lockdown Scope Mount Aluminum 1 Inch Black 2300596

    Reply

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