Base screws sheared off

[Petersen]

Is this why people upgrade to 8-40 base screws? Gun is a 338 edge. Probably has 400-500 rounds through it. The current load was not hot, cases eject easy, no ejector marks, etc. but some loads had been hot in the past and the reason for trying some new loads. How many people have seen this happen? New one to me.

 

[isaaccarlson]

If they were tight before shearing, I would say they were too tight. It doesn't take much to stretch a tiny screw and the clamp loads are much higher than people expect. Were they installed with a torque wrench? If so, how tight?

Were they china screws?

 

[Petersen]

Nightforce mounts and screws. Torque wrench was used. Scope has been mounted for around a decade

 

[cjl2010]

Heavy scope big recoil

 

[Petersen]

Forehead a bit sore as well. Lol

 

[isaaccarlson]

Nightfirce scopes are heavy. I would have expected it to happen sooner if that was the case. That action is very shiny, so there is practically zero friction between the bases and the action. I would mask off the area where the bases sit and sand it with coarse paper to roughen it up, then cold blue and put new screws in. That would go a long way in adding friction.

 

[isaaccarlson]

A friend of mine brought me his 30-06 that was not shooting well. He had gone after the scope screws but didn't check the bases. The screws were all loose and it had been hammering on the locating pins for some time. The front screw started it because it was too long. I fixed the pins, degreased the holes, cut the screws down, and used loctite. I torqued them down and remounted the scope. It should be good to go now.

Loctite and proper torque are important. A good surface finish is just as important.

 

[jimbires]

this is another reason to bed the rail to the action .

 

[BillLarson]

If you,ll look closely at pics.The mount was made for 8-40,s....front of mount is beveled.looks like it was hitting the recoil lug.
Drill and tap receiver 8-40 and bed properly fit mount.

 

[Varmint Hunter]

That didn't even happen on my 460WBY and I mounted the hardware many years ago without bedding or the use of a torque wrench.

I'd increase screw diameter and bed the base this time around.

 

[DoneNOut]

I never imagined this could happen. Wow, makes a guy rethink the rail mounting process. Thanks for sharing this unfortunate experience.

 

[DoneNOut]

this is another reason to bed the rail to the action .

What is used for the compound?

 

[sedancowboy]

What is used for the compound?

I use JB Weld or Devcon

 

[Petersen]

Appreciate all the comments. If I can get the screws out of action, I may try to rough up and bed base with the factory size #6 screws. If they are too
Much of a struggle it will be mailed off to someone to open up to #8 and I will still bed rail to action. My wife's bull elk tag opens nov 6. But I do have have other rifles as well.

Interesting comment about the base being designed for #8 screws. I'll look over the parts closer. The base and screws and rings were all factory nightforce.

This was an eye opener for sure. Now I really know why some bases and actions have pins, or better recoil lugs on rails to the action, larger screw upgrades, etc.

Sucks also because after the scope hit me, it hit the ground. The objective of the scope, the tube is wrinkled a little but glass looks good.

I honestly thought the gun exploded when it happened. But once I got some of my bearings back, I could see it was just the scope.