this is probably a stupid question but here goes. i have been mounting scopes for 30 years and cant remember andy problem like this before. the last two guns the back screw in the bases has stripped. the last gun was a kliengunther with leupole bases and now a steyre withe the same type of bases. the screws are new and the lsat gun has only had one other base mounted on it before. the screw is starting to round the threads before it ever starts to pull down to the base. does either of these guns use metric screws and not the regular screws that come with the bases from leupole? am i doing something wrong?

Welcome to the forum 735. Rules are simple, be nice and join in. Boy thats a tough question, I'm not sure if those would have a metric thread or be tapped in our standard 6 by 48.

If you've stripped the hole in the rifle I'd suggest having it redrilled and tapped to 8 by 48 and then drilling the bases for this heavier mounting screw. I've done this to a bunch of heavy recoiling guns. Another suggestion is to simply run a 6 by 48 tap into the screw hole and clean it up. You need to be really careful with that as if it is a metric thread it'l mess up the original.

You can give the rifle manufactures's a call/email and see what the screw specs are and you also might check with Brownell's tech section, there a wealth of info and also have the correct taps and drills and screws to go to the 8 by 48 if you need to.

Welcome.

I don't suppose you have access to the original hole-filler screws, so you could measure the threads? If you have a set of number drills, you can use the shanks to find the thread inner diameter to learn what the tap drill was, which will provide a clue. You can fill the hole with mold release and put enough 5 minute epoxy putty on the tip of a toothpick to set it in and get a thread impression to measure. It only needs to be clear on one side. Once you've made the determination, you will want to get a bottoming tap not only to clean up the hole that rounded the screw, but for cleanout of any putty bits that get stuck.

Thread gages are available from a number of sources. This is one: Enco (http://www.use-enco.com/CGI/INPDFF?PMPAGE=297&PARTPG=INLMK3&PMITEM=615-6324). You can get a 4-80 TPI gauge for $15 and a 0.25-2.5 mm pitch gauge for $4. Those will cover you. 48 tpi is about 0.5mm.