Description
Making a few checks along the way and taking necessary precautions installing Weaver scope bases will help keep the base secure and also help safeguard the screw holes from stripping out. Normal maximum thread contact is about 4 1/2 threads in Contender barrels. With less than 4 threads of contact, there is an increased risk of the screws stripping out due to over tightening, high recoil, or simply bumping or jarring the scope and mount. (Note that the TC "Duo Mount" is especially lacking in thread contact, so use caution with this design deficiency.) Holes should be tapped out with a "dead bottom" tap. This picks up about 1/2 turn of thread contact, but is best reserved to those experienced with tapping small blind holes. See the "More Advanced" comments below. The Weaver screws that come with the bases have a projection on the bottom end of the screw that is smaller and not threaded. This limits how far the screw can go into the hole and should be ground off. When I convert the bases to 6-screw, I cut the countersinks deeper and use different screws normally. I also have a special set up just for grinding screws to length with threads all the way to the end. An individual can do this himself, also, on a bench grinder or with a Dremel type hand grinder. When installing a Weaver base, be sure to tighten down each screw individually, then try to wiggle the base. If each individual screw does not hold the base down tight, the offending screws must be shortened so they do. Each screw tried should then be removed and examined for 1) deformation at the tip from bottoming out in the hole or threads not going far enough to the bottom of the hole and 2) marks on either the under side of the screw head or on the tapered part of the countersink in the base, indicating the screw is pulling down tight in the countersink. If there is deformation on the tip of the screw and the hole has been tapped all the way to the bottom, then grind some off of the tip a little at a time until the screw does pull down tight with no deformation of the tip. If you put a screw in the base, then hold the base up at eye level, sighting across the underside of the base, side to side, the tip of the screw should come just about flush with the bottom edges of the base. On barrels that have not had the holes tapped out all the way to the bottom, the screws may need to be very slightly above the bottom edge of the base. If you will then sight down the underside end to end and count the number of threads exposed on the bottom, you should come up with at least 4 threads. They are hard to see, yes, and a magnifying glass may be a must. You can also use a knife edge to follow the ridges of the threads down, following the crest and counting each thread as you go. Bolts and screws should always have a length of thread contact that is at least equal to their diameter, and if you will do some measuring, you will find that it takes this approx. 4 1/2 threads to achieve it on the 6x48 base screws.