Custom Ruger Model 44 Scope Base.

Where a rifle is designed for a two-piece scope base and the customer wants a one-piece base, it's time for some serious searching. Here's how I adapted a one-piece scope base to a Ruger .44 Magnum rifle.

A hunter presented me with his Ruger Model 44 chambered in .44 Remington Magnum. He tried, to no avail, in locating a one-piece Picatinny base for mounting an Aimpoint red dot sight. If possible, he also wanted to retain access to the open sights on removal of the quick-detachable optic.

This turned out to be a rather challenging request, but I keep bumping into this sort of situation a lot. A close look at the top of the receiver and the back end of the barrel showed three pairs of screw holes, all with apparent hole plugs. The front pair located on the barrel and the rear-most pair located near the base of the receiver had 6-48 size hole plugs. The central pair of holes on the receiver were larger screws with 82-degree heads. Curiosity found me removing one of these screws which weren't screw hole plugs. They appeared to have a function in holding something in place as some sort of bolt guide inside the rifle. Upon discovering another 6-48 deep thread hole, my immediate thought was to use this for an attaching screw if I could find a suitable one-piece base to span the distance atop the receiver. I could see where removal of both screws at once could be a mistake, so I removed only the front one.

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[ILLUSTRATION OMITTED]

The customer was still there as I searched through my assortment of one-piece scope bases. I came up with a Weaver Model #62, a 4.5" one-piece base. The base had two lateral slots each located near the end, and two sort of randomly placed pairs of screw holes. The bottom radius of the base would work out atop the Ruger rifle receiver. On placing the base over the receiver, a pair of holes near the rear third of the base matched perfectly with a pair of holes near the back of the receiver--a real stroke of luck.

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[ILLUSTRATION OMITTED]

Laying the base over the receiver so the rear holes lined up indicated all I would need to do is drill a hole in the base to match that of the hole where I had removed a screw in the receiver. There would be more than sufficient thread depth for a solid screw purchase at that point, as the screw continued to serve its function.

The customer could readily understand my plan and became very excited about the prospects of a solid, one-piece base on his Ruger carbine. It would involve cutting a pair of cross slots in the base for a solid mounting of the Aimpoint sight. This would also provide proper eye relief as mounted, also allowing a standard rifle scope to be used on the new base using regular rings if desired later.

Work Done Correctly

When it comes to mounting a scope, or any gun sight, absolute precision must be attained. Sights that move around from shot-to-shot leave shooting to guesswork at best, and this can often be traced back to the base or bases.

As a means of attaining a precision fit between the scope base and receiver, I remove minor imperfections by micro-lapping the base. This was done by moving the base straight forth and back along the top of the receiver with a sheet of 600 grit between the parts. A few linear passes over 3M paper does the trick. Using a paste-type grit for this purpose would mar the bluing on the receiver, which has a uniform, smooth surface.

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[ILLUSTRATION OMITTED]

The scope base was temporarily attached to the receiver with two 6-48 Fillister-head screws. A 90-degree scribe was then used to precisely mark the front base screw hole from inside the receiver with the bolt withdrawn. The base was then placed in the mill vise where it was drilled for an 8-32, 82-degree socket-head screw. The base was again attached with the three screws, making sure the screws didn't protrude beyond thread depth. It is well, however, to get all the screw-length possible as bases are mounted, but over-length screws can get you in trouble. In the case of a long front screw here, the bolt would bind or fail to close. Tolerances needed to be quite close.

Milling the cross slots in the base was routinely performed on the milling machine. I also enlarged the back slot for rearward mounting of the Aimpoint sight. The two more centrally located slots were spaced an inch apart at a width of 0.194". Normal Weaver slots are 0.145", as are many of the Picatinny style slots.

Mounting The Aimpoint

The Aimpoint sight has a unique, knurled, adjusting knob which is turned finger tight until a spring-loaded clamping mechanism slips at correct torque. This prevents an over tightening of the knob. Good idea. Haven't we all encountered overly tight screws and knobs or scope turret caps?

This sight base allows proper eye relief, which is not critical with the Aimpoint sight. The standard leaf-style open sight remains usable while viewing over the newly-mounted base when the Aimpoint sight is removed. Standard scope rings also can be used to mount a regular scope sight on the new one-piece base.

Conclusions

In this case, finding and adapting a one-piece scope base on a rifle not designed for this was a real plus. Sometimes a one-piece base will require custom fitting to the gun, along with relocation of screw holes in the base and/or the receiver.

Article Details

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Title Annotation:	BENCHWORK
Author:	Johnson, Norman E.
Publication:	American Gunsmith
Date:	Jan 1, 2017
Words:	948
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