Receiver Side Base For The Model 70 Winchester

This treatise will deal with reapplication of a receiver side base on a Model 70 Winchester rifle brought to me with stripped base screws after a second attempt was made to mount it. The rifle was a post 1964 M70 and wore a black synthetic stock that was used by Winchester for awhile, featuring a full action castin aluminum bedding block typical of those made by Bell and Carlson.

This bedding block allows better use of the center action screw than the typical stock of Pre-1964 vintage or any later stocks made of wood. With these, any over tightening of the center action screw causes a springing of the action in this area, leading to unpredictable accuracy and bullet point-of-impact. Close inspection of the side of the action revealed an abortive attempt at mounting the base.

There were a pair of plugged screw holes immediately forward and a few millimeters below a pair of drilled and tapped holes. There was one big problem. Both of the secondary 6-36 screw holes bore stripped threads. This is how the rifle was presented to me. When asked by the owner what recourse we had, I immediately thought of the Brownells 8-40 Screw Conversion Kit. Brownells offers a screw conversion kit to strengthen the normal 6-36 size with a stronger 8-40 screw replacement.

The Tactical Scope Base Conversion Kit contains all that’s needed to do many scope base conversions. This includes an 8-40 taper and bottoming tap, numbers 28 and 19 wire gauge drills, an 8-40 Fillister counterbore and a dozen each of 1/4-inch and 3/8inch socket head screws. The kit also contains a Brownells Screw Holder Gizzie to hold screws that may require shortening. Making The Conversion The Trakker target sight is made in England by RPA International

Ltd. and utilizes a rectangular base shaped to the radius of the left side of the Model 70 Winchester receiver. The part has a provision for four base screws to accommodate frontto-rear positioning on the receiver. Two of these base screws are used for normal attachment. Above the base attachment screws there are four tapped screw holes to select from in positioning the adjustable peep sight to fit the shooter’s sight viewing. A single slotted, threaded thumb screw is used to attach the sight to the base.

As received, the sight fit the customer’s normal shooting position requiring no relocation of the existing pair of stripped screw holes to position the sight at 90 degrees to the bottom of the receiver. The stock had a mortise to fit the sight base so work in this area was not needed. The action was removed from the stock and placed in a milling/drilling vise in preparation for screw hole re-drilling and tapping.

The later Model 70 Winchester receivers were not case hardened so drilling and re-tapping for the new 8-40 screw was pretty much routine. The existing base screw holes were in line with the newly tapped holes and the base holes were redrilled to the larger hole size and countersunk for the larger screw head sizes. The base was then tried This picture clearly shows the two replaced attaching screws that hold the sight base to the receiver. for fit and securely attached to the rifle.

Conclusion At a low cost to the customer, the re-tapping and screw head enlargement process required to correct the first attempt to mount aside base on a Model 70 Winchester rifle was essentially uncomplicated. The availability of Brownells handy screw conversion kit helped make this possible. AG