Re-threading receiver holes?

[Ray B]

I have a 1916 Mauser Model 98 GEW that I had rebarrelled and had a German era side mount installed. Recently I broke one of the windage screws, so removed the mount, only to learn that the gunsmith that drilled and tapped the side of the action for the mount apparently used SAE threads and the screws appear to be Metric. the threads on the screws are flattened due to cross threading as they were screwed into the receiver. Since the mount needed repair and new screws, at this point my plan is to order another mount and have it installed to the receiver by a more qualified gunsmith.

So the question is: the first effort would be to rethread the receiver holes to match the screw threads- but if there is insufficient metal to properly support the screws, what options do I have for filling in the removed receiver metal so it can be properly threaded?

 

[Ray B]

 

[Shootist43]

I'm not a gunsmith & they might have other or better ideas. I would think your first option would be to install a helicoil. this might mean re-drilling and tapping the holes as necessary. Another option would be to carefully plug weld the holes (perhaps via a tig process) and start from scratch. The cheapest method would be to drill out the existing holes as necessary and tap them for an oversized screw.

 

[GuttormG]

Next bigger size screw..

 

[Hogpatrol]

Stranger things have happened but I would doubt very much if a good gunsmith would mismatch screws. It looks like there's enough metal to go with a larger screw but then the mount would have to be modified, i.e. the holes and counterbores would need to be enlarged to fit the new screws. If by chance the screws weren't correct, I would find a different gunsmith, one who has Mauser experience.

 

[Spooksar]

My local gunsmith drills out the holes on big bore rifles to 5mm, he has had many broken mount screws over the years and this seems to solve the problem

 

[Hogpatrol]

My local gunsmith drills out the holes on big bore rifles to 5mm, he has had many broken mount screws over the years and this seems to solve the problem

Have had a few heavy recoiling rifles, even after the correct torque and loctite, had scope base screws loosen. 5mm is roughly three sizes larger than most standard base screws, #6s, and should be plenty sturdy.

 

[Ray B]

Met with a young kid (about 30) who was very good at diagnosing the problem and listing the various options to correct it. Turns out the screws were the correct size, but the location of the holes was out of line, so the hole in the mount didn't line-up with the hole in the receiver, which meant that the threads on the screw were getting shaved off on one side as the screw was turned into place. Two holes work but the third one needs some work. So either I can use just 2 to mount it, which would probably work since it's a 7x57mm with not a lot of recoil or I can get the low portion of the hole TIG welded to add some material, then the new gunsmith can re-drill & tap the out-of-line hole. Oh well, the rifle is back in the rack as I mull over what I want to do with it. The silver lining is that I've made connections with a kid that won't be retiring before I die, so I can resume having things done without fear of getting a botched up job.

 

[Bob Nelson 35Whelen]

I have a 1916 Mauser Model 98 GEW that I had rebarrelled and had a German era side mount installed. Recently I broke one of the windage screws, so removed the mount, only to learn that the gunsmith that drilled and tapped the side of the action for the mount apparently used SAE threads and the screws appear to be Metric. the threads on the screws are flattened due to cross threading as they were screwed into the receiver. Since the mount needed repair and new screws, at this point my plan is to order another mount and have it installed to the receiver by a more qualified gunsmith.

So the question is: the first effort would be to rethread the receiver holes to match the screw threads- but if there is insufficient metal to properly support the screws, what options do I have for filling in the removed receiver metal so it can be properly threaded?

@Ray B
Any good gunsmith can use a heat sink to fill the holes in and redrill and tap to your needs no problems.
Don't let bubba the blacksmith near it as they could stuff the action temper.
Bob

 

[fourfive8]

First, determine what the d&t holes are in the receiver... or as close as possible. If close to a buggered #6 then use correct pilot drill for a #8 then tap #8. If they are close to a buggered #8 then proceed to d&t for a #10. I wouldn’t go larger than a #10. A #10 is starting to approach “too big” for mounting purposes, IMO. So if holes are much larger than a buggered #8, I’d probably seek a good gunsmith with experience in welding/filling holes- then start over.

 

[Ray B]

I'm thinking that i'll go with the two holes that are properly aligned, then machine off part of the screw so that it will fit into the third hole, then after coating the area with release agent, epoxy the hole with the thinned screw in place. Since it's a 7x57 the recoil shouldn't be a problem for shaking things loose.

 

[Wyatt Smith]

Do they make Helicoils that small?

 

[sestoppelman]

Another golden oldie!
Were it mine Ray, feeling as I do that side mounts are an abomination from Hell, I would plug those holes however I could, and D&T the top properly.