Conetrol | Projectionless Scope Mounts

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Bases for Scopes with Short Mounting Tubes

Compact scopes on long actions often present mounting problems: our standard base may position the rings too far apart for a short-tubed scope. For these situations, we provide alternative 2-piece bases. This generally involves a special front segment that puts the front ring as far back as possible, sometimes overhanging slightly the shell-ejection port.
Because of this slight overhang, most people would probably prefer a standard base. A Ring-Extending or Short-Ring-Spacing base will also work with long-tubed scopes, however, and could provide a more rearward scope location if that's what you need.

Cone Screw Tightening

Our fine-threaded socket cone screws can exert much more pressure than necessary for even the most jolting recoil. Tighten only enough to prevent scope slippage. A good rule of thumb is to tighten with the wrong end of the wrench first (using the short end as a handle) before flipping the wrench around and tightening just a little bit more with the other end. If your scope does not slip under recoil, the cone screws are as tight as they need to be.

DapTar Bases for Dovetailed Receivers

Conetrol makes a variety of DapTar bases that attach to guns with dovetailed receivers. Generally speaking, the receiver dovetails should be open-ended so our bases can be slid onto them.
One thing we've learned over the years is that dovetail sizes vary from gun to gun. On a number of occasions, we've taken the same base and tried it on different rifles of the same make and model, finding it about right on one gun, a bit tight on the second, and loose on the third. Our instructions packaged with DapTar bases suggest filing or peening the dovetailed angles on our bases (if necessary) for a better fit to individual receivers. A triangular file works well for enlarging dovetails.
For a tighter fit, you might prefer using a vise rather than peening. Find a steel rod or pipe at least an inch in diameter and place the base segment astraddle the rod/pipe. (If you can't find a rod or pipe, a bolt with a stack of 20 or so large-diameter washers will also work.) Pad the segment to protect it's finish and put the segment and rod/pipe in the vise. Use the vise to force the rod/pipe against the inner edges of the base dovetail, forcing the dovetail edges up and into the base segment. Alternatively, shims that raise the base slightly in the dovetail may also provide a tighter fit.
Some rimfires have the standard 7/16"-wide rimfire dovetail, but are also drilled for a conventional top mount. Many of our customers find the RFDT/RFDTX dovetail bases more attractive, as the sides of the radiused, screw-down base necessarily overhang the dovetail cuts in the receiver. If you decide to go with a dovetail base, you might opt for the RFDTX base if your receiver is very short and you need to locate one of the rings past the end of the receiver dovetail. Receivers that are pressed rather than milled may be too high in the middle for our RFDT/RFDTX bases to seat properly. A thin grinding wheel can relieve the underside of our base segments between the dovetail edges to correct this.

Mausers

It is customary for gunsmiths to rework the bolt in customizing military Mausers. Both our bridge (LRM-1 and SRM-1) and two-piece (LRM-2 and SRM-2) bases for these actions are made to fit up against the clip-guide hump without further alteration of either action or base. To accomplish this, we make the rear screw-hole spacing of our two-piece bases 7/16” instead of the normal half inch. In general, all that’s required is drilling and tapping the receiver and screwing down the Conetrol base. So if your gun is already drilled and tapped with holes a half-inch apart on the bridge, you should use our FN/J9 or HVA/CG two-piece bases: FN or J9 on the large-ring Mausers (1.400”) and HVA or CG on the small-ring Mausers (1.300”). These bases should also be substituted if the clip-guide hump has been ground down, half-inch hole space permitting. The J9 and CG bases will prevent overhang at the rear of the receiver ring if the front holes have been drilled farther back (less than 1/2” from the ejection port).

Return to Zero: Removing Your Scope

Although the Conetrol mount permits the scope to be removed and replaced (with return to zero) if our Limited or Custum rings are used, the Conetrol mount was not specifically designed for this. It was designed as a low, solid top mount to complement the finest guns made. Like other mounts of its genre, it was meant to be "permanently" installed and fully integrated into the gunmaker's artwork.
Nevertheless, directions for removing the scope and returning it to zero are included in the instruction sheet packaged with each Conetrol base. Since all four cone screws must be loosened, the process involves marking one of the cone screws under each ring so that it can be turned back to its original position when the scope is replaced. The return to zero is very accurate, but the process is a bit more complicated than with some other mounts.
If you desire a mount that will readily allow use of iron sights, you should consider either (1) a side mount (scope positioned to the left of the action), (2) a see-thru mount (scope positioned high enough to allow use of iron sights), (3) a swing-over mount of the type once made by Weaver and Pachmayr, or (4) a lever-type, quick-detachable mount.

Ring Unscrambling

Each Conetrol ring is assembled and polished as an intact unit, giving each ring its perfect fit. Parts from different rings generally don't look well together. If your ring parts become mixed, use the following hints to help you get them sorted out again.
1. A number is stamped on the bottom of one ring half and not the other. If you get two numbers together or two no-numbers, those halves do not belong together.
2. A cap-locating notch is ground at the top of one ring half and not the other. If you get two notches together or two no-notches, those halves do not belong together.
3. Hold the ring halves in position together and look closely at the top and the bottom. Unless the width is exactly the same at top and bottom, those halves do not belong together.
4. Each ring is bored before it is split. The interior boring marks are generally discernible and should continue across the splits from one ring half to the other, both at top and bottom, when the ring halves are held in position together. If the boring marks do not coincide, those halves do not belong together.
5. In the finishing process, the circular dovetail at the top of a set of ring halves is relieved fore and aft with a hand grinder so the cap can be put on. This is done in a single operation with the top edges of the ring halves pushed together as if in position around a scope tube. If it is obvious that the halves of a split dovetail atop a set of ring halves were not ground together at the same time, those ring halves do not belong together.
6. Circular machining marks are usually discernible at the top and/or bottom of each set of ring halves, which may change slightly from one ring to another. If such machining marks are discernible at either top or bottom of one half, the same pattern should be visible on the other. But if the cut is very smooth at the top or bottom of one ring half, it should be smooth on the other. If such is not the case, those ring halves do not belong together.
7. Once you have a pair of ring halves you know belong together, put on a cap and check for good fit. With the locating notches of the cap and ring half together, the fit should be precise, with the small flats at the front and back edges of the cap lining up exactly with the front and back edges of the ring. If the cap overhangs even slightly or is not quite as wide as the ring, that cap does not belong with those ring halves.
8. If, say, you are trying to sort the parts of two rings and you believe you finally have the right cap on the right set of halves, try switching the caps. Sometimes a pair of caps may look "good enough" on a pair of rings, but may look just right if you switch them. Then, you know your rings are right!

Ruger No. 1's

For the Ruger No. 1 that does not come with the Ruger quarter-rib, Conetrol makes two-piece bases that attach to the screw holes drilled in the barrel.
For the Ruger No. 1 provided with the quarter-rib, Conetrol makes two types of bases: (1) a DapTar base that fastens to the Ruger mounting cuts on the rib and (2) a rib-replacing base that uses the rib's screw holes after the rib has been removed. Neither type of base requires drilling or tapping for attachment.
The DapTar base (RUGDT-2) is available in two-piece design only. Both segments may be attached with the scope rings positioned either 5/16” before or after the quarter-moon cuts in both sides of the rib placed at the Ruger factory. Base height is 0.275”, which permits emergency use of the iron sight on the Ruger rib if the scope is detached. Each DapTar base comes with recoil dogs that engage the crosswise, concave slots atop the Ruger mounting rail. These devices tame the most vicious recoil.
The rib-replacing base (0.401” high) is one-piece and uses the two rearmost screw holes in the Ruger barrel and the recoil stud between them. This Conetrol base has a hole in its bottom that engages the recoil stud when the base in screwed down into place. Plug screws are packaged with each Conetrol base for the front two screw holes. The front recoil stud may be left as is, removed and stored with the rib, or ground flush with the barrel.
Ring spacing on the rib-replacing base is less than four inches, which allows mounting of even compact and short-tubed variable scopes. It positions the rear Conetrol ring over the receiver ring of the No. 1, allowing the scope to be located further back where it really ought to be.

Solid Rings: For Scopes with Straight Tube Ends

Conetrol's solid rings can only be installed on scopes with straight tube ends. Scopes with enlarged ends require split rings. Since solid rings come in the same heights as split rings, a solid ring and split ring may be combined on a scope with one straight end. Just be aware that your solid ring may suddenly become useless if you ever decide to switch scopes.

Special Combination Bases: If Your Gun Isn't Listed

If your gun is not in the Conetrol stock numbers list, but will take a conventional screw-attached top mount low over the receiver, we can probably provide a two-piece base that will fit it, even if it the mounting holes on your gun were not drilled at the factory.
To help us provide a mount that will work:
1. Tell us if your gun's receiver is flat on top, or give us the radius of the receiver where each base segment would sit. If you're not sure of the radius, cut out the edge of a card to match the unknown radius (or radii) and send that in.
2. Lay a piece of paper on top of the receiver and rub with a pencil to show the configuration of the top of the receiver and where the screw-holes, if present, are located.
3. If the front and back part of the receiver are not the same height, give the difference in height.
4. Draw a rough sketch of your gun showing where the mount will be located, with dimensions, etc.
We cannot be positive that we can fit your particular gun, but the above information will help us find out. It may require drilling/tapping another hole or two in the receiver.

Steyr Zephyrs

Early Steyr Zephyrs had a very short front dovetail (about a half-inch long) with a hump in front of the dovetail. Most of these short dovetails were about 5/8-inch wide (16mm), but some were rimfire-like dovetails about 3/8-inch wide (11mm). Our standard front base segment for either short dovetail overhangs the shell-ejection port.
To address this, we've shortened some of our existing bases to reduce the overhang as much as possible. These are our LSAZDT and RFZDT series of bases for 16mm- and 11mm-wide dovetails, respectively. But if the front dovetail on your Zephyr is about an inch long, you should use our standard LSADT or RFDT (or RFDTX) base.

Winchester Model 52: Old and New Versions

The original Model 52 Winchesters were made with .500" rear hole spacing and .960" front hole spacing, center to center. The Conetrol stock numbers 52-1 and 52-2 identify bases that match these hole spacings.
Later, Browning reproduced the 52 Winchester, but drilled-the receiver with .860" hole spacing, both front and rear. Winchester then offered the 52 Winchester with the same hole spacing in front and rear (.860", center to center).
Unfortunately, the Browning and new Winchester versions of the 52 Winchester have very high bolt throws. While Conetrol makes two-piece bases that would fit these rifles (45T559-2, where the hyphen is H, G, L, or C for Huntur, Gunnur, Limited, or Custum), most Conetrol rings would probably not be high enough to keep the bolt from hitting the scope's eyepiece. We hope we have solved this problem with our Extra-High rings.

Winchester Model 70: Variations Over the Years

Most Model 70 Winchesters are made with 0.860" hole-spacing, center to center, on both the receiver ring and bridge. Early .300 and .375 H&H Magnums, however, had 0.330" rear hole-spacing.
Later, the standard action was used for even the largest cartridges, including the .300 H&H, the .375 H&H, and the .300 Weatherby Magnums. Now, 0.330" rear spacing is again being used for the largest cartridges. The rear bridge section on these actions with 0.330" spacing is noticeably shorter than the front receiver ring section.
For the newer, short-action Model 70s made for smaller cartridges, Conetrol can provide only two-piece bases. Bridge bases are optional for all others.
Pre-64 Model 70s have dual 0.860" hole-spacing in standard calibers, but 0.435" rear spacing in .300 & .375 H&H Magnum. There were also some "30-06 Target" Models with 0.435" rear spacing.
Pre-war Model 70s (and Mod. 54s) can be recognized by a shallow longitudinal trench in the top of the bridge (rear part of the action). Conetrol mounts for pre-war Model 70s all have 0.435" rear hole-spacing regardless of caliber.
The bolt throw of current Model 70s is lower than in pre-64 models, and Conetrol Low rings can be used if the scope's objective will permit it. Earlier Model 70s generally require our Medium or High rings to clear scope eyepieces.
To be sure we send the correct base, always tell us the distance between all screw holes, center to center. A quick ruler measurement will do.

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