Base screws sheared off

[DoneNOut]

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 screen 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.

I can certainly relate to that feeling when shooting! I took a 45 ACP slug ricochet right between the eyes in 2004. I thought the brass ejected hard at first, but then realized my bell was rung so bad it had to be the bullet. I took some jacket to the shoulder too. Took a few seconds to figure out what happened. I shot at a steel IPSC plate that had holes shot in it from a dummy with an AR15. I did not know dents and holes in a steel plate could spin a bullet 180 degrees and back at the shooter.

 

[jimbires]

What is used for the compound?

I use the original JB weld on scope rails , it's the slow dry . it's supposed to be stronger than the quick dry blend . you could use devcon , marine tex , or any of the other bedding compounds . JB weld is just easy for such a small amount that's needed .

 

[Petersen]

Got the screws out of the action. Time to learn some base bedding. I have devcon on hand.

 

[Petersen]

Watch Broz's video and grabbed some JB kwikweld. Hope this holds !

 

[jimbires]

here's some old instructions . before the bedding sets up , I use a Q-tip dipped in WD40 to clean up what has squeezed out around the rail . I do not roughen up the surfaces . I do clean everything with denatured alcohol .

 

[BHP9]

I place a drop of red LocTite 262 between the screws and just ahead of the rear base and never had a problem. To remove the base/s just strike them with a plastic tipped mallet from the side and with a slight upwards direction.

 

[ntsqd]

If you 'ring' two high quality gauge blocks together (basically slide them together) you can not pull them apart. You have to slide them back apart, and it isn't always easy to do that. The lesson here is that two very smooth surfaces that match each other exactly (like you get when bedding a base to an action) do not need to be roughed up. It does help that both gauge blocks are made from the same material, however it is not an absolute requirement that they be for this to happen. The biggest problem is that #6 screws are just too small for some applications. Their max torque does not generate enough clamp load for the shearing forces involved. Even #8 screws do not have enough shear strength for the forces involved, but they can generate enough clamp loading of the base to the action so that the screws will never see a shear loading.

Leave the action finish alone, bed the base, and torque quality screws into place with Lock-tite 243 (it's more tolerant of contaminants than 242).

 

[Lionel Boyd Johnson]

I experienced a sudden loss of zero on a very light 7-08 with a Leupold VX3, 3.5-10X in Talley mounts. Found three of the four mounting screws sheared off. The screws were those supplied by Talley with the mounts, installed with low strength (small screw) Locktite. After getting the broken off ends out of the receiver, I remounted using new screws from Brownells, ground to proper length. I have not had a problem since. My gunsmith told me he never uses Locktite, but does always use a torque screw driver.

 

[distantfoe]

Have a gunsmith add press pins and be done with it.

 

[Wedgy]

After dealing with loose bases/rings/scopes I drill out to #8 screws, pin all rails, and bed w/o release agent(it's easy to get off with a heat gun), rings are lapped and bedded.
Lots of info in this thread;

Light rifles, big cartridges, and scope mounts - learned my lesson, now it's time to pass it on.

I'll start this thread by saying that I am in no way bashing on the manufactured of the scope mount I used, it is in no way the mounts fault, but instead my fault for not choosing the appropriate mounting solution for the extreme situation I put it in. The mount I used is a quality piece of kit...

www.longrangehunting.com

This is from Shep;

"Just pin it. I use a #31 drill bit in a drill press. Drill right through the base into the receiver. Don't go all the way through the receiver. I usually put them right between the mounting screw holes. After drilling this .120 diameter hole take an 1/8 drill bit and cut a few pins from it with a cutoff wheel. This is .005 bigger than the hole you drilled. One drop of red locktite and tap the pins in. A small chamfer on the bottom of the pin helps it start in. Practically anyone can do this. These pins are much stronger than screws. I do all my actions like this. Go to 8-40 screws and pins. All on a bedded base. No more problems.
Shep"

 

[ILVTOHT]

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.

My sons 338 RUM did exactly the same thing. I tapped out the screw holes to 8-40 and JB welded the NightForce 8-40 base to the action. No more problems!

 

[skipglo]

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.

Mine either! But I would assume they were dramatically overtorqued causing fractures that just took this long to shear! I glad to hear you weren't badly hurt!

 

[Petersen]

Mine either! But I would assume they were dramatically overtorqued causing fractures that just took this long to shearover torqued. Always torque to specs. I believe they started to work loose but the gun was still holding under MOA. The finish inside the base holes and on bottom show it was moving just a little bit.

Mine either! But I would assume they were dramatically overtorqued causing fractures that just took this long to shear! I glad to hear you weren't badly hurt!

I think they were just working loose a little. Not really loose because the gun shot under 3/4 moa less than ten rounds before the screws sheared. Usually torque to specs but it has been a decade since messing with the base on this gun.

I did not rough up action or base. Used kwikweld and no release agent.

Shot two loads last night. The first shot was off target, figured out it was low and adjusted. Next two shots cut each other at 200.

The next load had two touching and one off an inch or so but it was also windy.

I think the gun will be ready to go in a week
Or so.

 

[Rosebud]

You mentioned that the scope tube has wrinkles in it. That may be really bad. When you remount it check your tracking and make sure it holds a zero. Seen something similar happen with small dent in the tube that required a Leopold to get returned. The tube was bent.