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Scope Mount Design

Scope Mount Design

Take pity on the poor manufacturers of scope mounts. They try to help shooters attach telescopic sights to rifles. A worthy cause, but when somebody heads to the range after screwing everything together, sometimes the rifle shoots so far off, the scope’s adjustments can’t get the bullets anywhere near center. And after the guy takes everything apart so he can return the mounts for a refund, the stupid rings have left a bunch of dents and scratches on the tube of his new $500 scope!

In reality, at least 90 percent of the time the problem is the top of the rifle’s action tilting this way and that, due to over-enthusiastic polishing at the factory. Or the scope mount holes are drilled off-center, or the barrel threads aren’t exactly concentric with the action. As for the “ring marks,” some scopes have slightly over-size tubes, and not all are cheap! But the scope mounts get the blame.
When scopes were first attached to rifles this problem didn’t really exist, because scopes were very long. They had to be, since the lenses of the day didn’t bend light very well. Some scopes were even as long as the rifle’s barrel, so they pretty much had to line up, and high-magnification “target” scopes stayed around until well after World War II.

Hunting scopes, however, got shorter well before the war, and eventually ended up in mounts 3 to 6 inches apart. With a 3-inch ring spacing, a misalignment of 0.01 inch results in a point-of-impact change of a foot at 100 yards. The average business card is about 0.01-inch thick, so a little error in rifle action polishing or machining can make a big difference.

Many scope-mounting holes aren’t drilled precisely either. It’s especially difficult to get two holes only 1/2-inch apart exactly in line with the barrel—assuming the barrel’s aligned correctly in the first place. I’ve seen the muzzles of 24-inch barrels almost 1/4 inch out of line with the center of a bolt action.

As a result, when making bases and rings for factory rifles, manufacturers must make them to fit an “average” rifle, but can’t account for every variation. In fact, one maker, whose precise bases and rings appear on many fine custom rifles, refuses to make mounts for one very popular factory rifle because that rifle’s actions vary so much he knows shooters from Alaska to Arizona would complain about his mounts.

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The most common type of scope mount uses bases screwed to the rifle,
then rings clamped to the bases.

The Redfield System

However, there are ways for scope mounts to compensate for variations in rifle actions. One of the most popular mounts made, the design once known as the Redfield (now more often called Leupold) uses a front ring with a bottom dovetail. The dovetail rotates into a slot in the base, and the rear ring fits between two opposing screws on the base. Turning these “windage” screws back and forth aligns scope with the barrel of the rifle.

This is one of the oldest scope mount designs around. John Redfield started making iron sights in 1909, but 5 years later started making scope mounts, and by the 1930’s was producing the “Junior” mount, basically the same system produced by Leupold and several other companies today. At first scopes didn’t have any internal adjustments, but in the first half of the 20th century most had internal elevation adjustments, but some didn’t have windage adjustments. Consequently scope mounts were expected to make any necessary right-to-left changes.

Lack of internal windage adjustment lasted longer in European scopes than in American ones. In fact, when Swarovski started making scopes in 1952, some of their models lacked internal windage. Until about 1950, very few factory rifles from either side of the Atlantic were drilled and tapped for scope bases, and the job was done by gunsmiths of varying skill. Windage-adjustable mounts were essential not just for some scopes, but to compensate for varying scope screw holes.

By 1960 most hunting scopes had internal adjustments, and just about all factory centerfire rifles came drilled and tapped for mounts. Consequently, some shooters aren’t aware of the purpose of windage screws on Redfield-type mounts.

A friend of mine became a local hero a few years ago on “sight-in day” at a local range. Another guy started whining loudly about the new scope he’d just mounted on his deer rifle, since it didn’t have enough windage adjustment to get on a 2×2-foot target at 100 yards (a rare instance of the scope getting blamed, instead of the mounts). My friend noticed the guy’s scope sat at a noticeable angle on the rifle and suggested he could solve the problem with a screwdriver from his range kit. The whiner was suspicious at first, but eventually agreed. It turned out he’d simply tightened the left windage screw until it stopped, and the scope was several degrees off-line.

Unfortunately, Redfield-type windage screws don’t always hold the rear ring firmly. A number of years ago I was visiting Dave Talley in Glenrock, Wyo., before he moved his shop down to South Carolina, and he showed me his old .375 H&H. You’d think it would have Talley rings, but instead the scope was in Redfield mounts—and the rear ring had shifted backward at least 1/16 of an inch between the windage screws. “I don’t shoot it much anymore,” Dave said, “but I keep it around to show people what can happen on a hard-kicking rifle.”

In the Redfield system only the front dovetail ring has a firm connection to the base. It will hold scopes fine on rifles up to about .30-06 in recoil, but above that something sturdier works better, the reason several companies now offer mounts with dovetails on both rings. They’re very strong, but don’t always align the scope on every rifle. Burris’s Signature dual-dovetail rings solve that problem. They feature offset polymer rings inside the primary steel rings, allowing the scope to be adjusted in any direction desired, even up and down.

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European claw mounts have a front ring with two hooks that slide into slots in their base,
and a rear ring that clamps into its base, often with a spring. The rear ring traditionally
has windage screws, because until relatively recently, many European scopes didn’t have
internal windage adjustments.

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This Thompson/Center Icon has sturdy tactical rings clamped to integral Picatinny bases.

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The sleek Conetrol rings are attached to the bases with opposing screws,
delivering strength with windage adjustment.

Simple & Inexpensive

The other really popular mount is the inexpensive model made by Weaver. Their tip-off rings attach to cross-slotted bases via clamps tightened by a cross-bolt, and are simple and strong. The only mechanical problem is the top-clamp around the scope tube, with screws only on one side. Tightening the screws tends to tilt the scope slightly. If you install enough Weavers, it becomes automatic to start the scope slightly tilted, but a bunch of companies (including Weaver) make rings to fit Weaver-style bases with screws on both sides of the top of the ring.

Weaver Tip Offs aren’t the most esthetic mount in the world, but they work far better than many rifle snobs realize and can even be used as pretty precise detachable mounts. Unfortunately, like dual-dovetail rings, they don’t offer any flexibility to accommodate variations in actions.

Bushnell used to offer aluminum rings for Weaver bases with the scope holes slightly offset, so one ring could be turned around for some “windage.” Sometimes a Weaver ring or base isn’t machined quite the same as the other and the same thing can be tried.

I’ve even swapped the Ruger factory rings on No. 1 single-shots from front to back and found enough variation to solve occasional windage problems, but the rings on Ruger bolt-actions are of different heights, so trying-and-switching requires more than one set of rings.

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Some European rifles like this Sako come with deeper grooves on the receivers for scope mounts.
The rings on the Sako are Burris Signatures, with offset synthetic inserts allowing the scope
to be closely aligned with the barrel.

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Probably the simplest and cheapest mount is the Weaver Tip Off. It’s pretty strong,
and if the slotted nuts are tightened alternately and gradually, it is quite
repeatable when detached and reattached.

Spendy Claw Mounts

Another scope mount variation called the “claw” developed in Europe. The front ring has a pair of hooks (“claws”) on the bottom that fit into matching holes in the front base. The rear ring attaches with a clamp, often but not always spring-loaded, so the scope can be quickly detached. Claw mounts often have some sort of windage adjustment in the rear mount, and are usually put on rifles by precise German gunsmiths, who normally get them straight.

They do cost a lot, however. When several of us optics writers went on a tour of various Zeiss facilities in Germany 20 years ago, Zeiss had just introduced a new and improved variation of the classic claw mount. We stopped at a gun shop to watch one being installed, and stood there for half an hour while a gunsmith tinkered away.

The Zeiss tour-guide talked all the while about the mount’s many advantages, then asked if Americans would be interested in such an obviously superior method of mounting scopes. One of us asked how much it cost, and the answer was about $600, before the necessary gunsmithing charges, the equivalent of $1,400 today. Several of us simultaneously answered “No!” Americans prefer cheaper mounts we can install ourselves, even if we whine about them afterward.

One variation not often seen these days is the side mount. Used both in Europe and the US, side mounts were primarily developed for lever actions with top ejection, and bolt actions with a slotted rear bridge. Since no rifles come drilled and tapped for side-mounts, they also require a gunsmith’s services, one reason the very fine Griffin & Howe side mount isn’t seen very often anymore, though it’s still available.

Almost all modern scope mounts feature some variation on all these systems. Even the slick-looking Conetrol rings are essentially a clamp-on, though the opposing screws on each base also provide windage adjustment. And all except rings screwed directly to the action can be made more-or-less detachable.

The ability to remove and reattach a scope quickly was considered just about essential until after World War II, when scopes started being sealed against internal moisture. Before then scopes fogged frequently, and hunters often needed to use the rifle’s iron sights.

Another solution was mounts allowing use of irons without removing the scope. These also have several variations, the simplest a pair of holes through the rings under the scope, but tall side mounts were sometimes used. Their main disadvantage is the difference in height between irons and scope, preventing the same cheekweld when switching between them.

However, due to the lack of bases on top of the action, side mounts can also allow the scope to be mounted very low. Consequently the scope’s reticle could be very close to the same height as the rifle’s iron sights, and with the scope detached the same cheekweld also worked for the irons. One of the rifles in my collection is a custom Springfield with a very low-mounted Lyman scope in a detachable Griffin & Howe side mount, with the scope’s reticle only a fraction of an inch higher than the iron sights.

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Modern “tactical” rings are basically a very sturdy variation on the old Weaver design.
When clamped onto a Picatinny rail they’ll hold big scopes firmly even on rifles like
this Savage .338 Lapua Magnum.

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One of the most popular mounts in America was first offered by Redfield in the 1930’s.
It features a front ring with a dovetail that turns into a slot in the base, and a
rear ring secured by opposing windage screws. This particular mount was made by Leupold.

Integral Bases

All these mounts use bases screwed to the action, but some rifle actions have integral bases. These vary from simple grooves like those found on .22 rimfires to complex dovetails and slots like those found on CZ, Ruger and Sako centerfires, or Picatinny rails, either machined or permanently attached. Scope rings that screw directly into the threaded holes usually used for bases are a variation on the same mechanical theme. Both eliminate intermediary bases, so connect the rings to the action more securely, at least in theory.

For several decades easily detachable mounts went out of style, though some hunters of dangerous game always preferred them, believing iron sights were quicker and more foolproof on up-close animals that might be rapidly advancing. Today detachable mounts are making a comeback, especially with hunters and target shooters who travel a lot, in part due to larger scopes: It’s easier to pack a rifle inside an airline case when a big scope is removed. Plus, a spare scope can also be sighted-in and ready to go in another set of rings.

There’s a definite trend toward simpler mount designs, especially clamp-on rather than turn-in or claws. Most “tactical” rings made today are essentially very rugged versions of Weaver Tip Off rings, and the Picatinny rails on so many actions are variations of Weaver bases, even though the precise dimensions are supposedly slightly different. Most heavy-duty clamp-type rings use sturdy bolts tightened with hex nuts, rather than the slotted screws of Weaver Tip Offs.

Also, today, many if not most mount manufacturers recommend certain torque settings for the screws on their bases and rings, partly because too many scopes get crushed or marred by heavy-handed installers who assume tighter is better. As noted earlier, dents and scratches on scope tubes are almost always blamed on mount rings, but normally the fault lies with whoever mounted the scope. They don’t make sure everything’s lined up straight in the first place, then really crank on the ring screws to “make sure the scope doesn’t slip during recoil.”

Most scopes for really hard-kicking hunting rifles, however, will stay in place with the 15- to 20-inch-pounds recommended by most manufacturers. Knowledge of correct torqueing has resulted in a pile of torque drivers appearing on the market over the past few years, but these can vary considerably in quality. I recently talked to a guy who claimed one of his scopes slipped with 20 inch-pounds of torque on the ring-screws, so now he used 27 inch-pounds, but I would bet a new set of Talley rings his torque driver isn’t very accurate.

Installed correctly, today’s scope rings almost always work very well. If we understand the reasons for the ways they’re designed, we might not even blame them when something goes wrong!
By John Barsness

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Talley offers two basic types of mounts, steel rings that clamp to bases (above, top gun),
and an aluminum lightweight where the bottom half of the ring screws directly to the rifle’s
receiver. The best-known integral base system in America is on Ruger’s bolt-action and
single-shot rifles. Their stout steel rings (below) also work as detachables.

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Burris Company
331 East 8th Street
Greeley, CO 80631
(970) 356-1670
http://gunsmagazine.com/company/burris-company/

Conetrol
10225 State Highway 123 South
Seguin, TX 78155
(800) 266-3876
http://gunsmagazine.com/company/conetrol/

Leupold & Stevens, Inc.
P.O. Box 688
Beaverton, OR 97075
(503) 646-9171
http://gunsmagazine.com/company/leupold-stevens-inc/

Precision Reflex, Inc. (tactical rings)
710 Streine Drive
P.O. Box 95
New Brennan, OH 45869
(419) 629-2603
http://gunsmagazine.com/company/precision-reflex-inc/

Talley Manufacturing Inc.
P.O. Box 369
Santee, SC 29142
(803) 854-5700
http://gunsmagazine.com/company/talley-mfg/

Weaver Optics
1 ATK Way
Anoka, MN 55303
(800) 379-1732

http://gunsmagazine.com/company/weaver-optics/

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