Ring slippage

[tadge]

Gday Fellas,

I went down the range to sight in my 338LAP.

I'm running a VX3 6.5-20X50 in MK4 rings. After about 10 good groups the POI changed and I noticed my scope had slipped AFT (thats right AFT not FWD) by about 1/4inch.

The rings were lapped and torqued to 40in/lb.

40 in/lb is pushing the limits for the screws so I'm reluctant to screw them down harder.

Any suggestions?? I'm considering a 3rd ring.

Chhers in advance

Tadge

 

[Jon A]

40 is way more than necessary if everything fits together correctly. Check to be sure you didn't overlap them such that the ring halves are contacting each other instead of clamping the scope.

 

[tadge]

Gday Jon A,

Rings still have a few thou gap either side.

I'm a bit lost on this one.

Tadge

 

[esshup]

Was everything degreased before assembly?

Just to get an idea of recoil velocity, what bullet, speed, and wt. of the gun? You're right, I wouldn't torque the screws any more.

 

[tadge]

Gday Esshup,

Load is 97gr AR2225 behind a 250gr pill. Did not chrony this load but should give around 2850fps.

Have not weighed the rifle but should be around a total weight of 13lb.

I have taken the rings off and cleaned them was not any grease or oil underneath.

Tadge

 

[Gene]

Try a little powdered rosin under the rings. Do not overtorque and bend the scope tube.

 

[esshup]

Recoil velocity is approx 12 ft/sec and recoil is 29.5 ft/lb. (that's without a brake)

If you take the rings apart, double check that there is a gap, and check that the screws aren't pulling up the first thread out of the bottom ring, interfering with the top half tightening down if there's only a couple thou of clearance. The rosin is a good suggestion.

If you have a correct sized tap, I'd also check the bottom ring half to ensure that the threads aren't getting pulled out of shape. If they are, I don't know of a way to fix it other than going one screw size larger if you have access to equipment to do the job.

 

[RFears]

Mine is doing it too on .300 RUM. Switching to Nightforce 1 piece mount and see if that will work, don't torque over 25 inlb though. 40 is toooo much....

 

[Pdvdh]

Gday Fellas,

I noticed my scope had slipped AFT (thats right AFT not FWD) by about 1/4inch.

Tadge

You must have a brake on the rifle? I've never had a scope slide back toward the shooter on any non-braked rifle. Mine always creep forward in the rings, when they have crept.

I've not had a scope creep on a braked rifle yet, so I don't know if backward creep is an issue with muzzle brakes or not.

The heavier the scope is, the more likely a scope creep problem. If the bottom half of the rings have been lapped to a good fit with the scope tube then you may need to add a third ring. Lapping that third ring could be interesting unless it lies in the same plane as the existing two. I've heard of both rosin and lock-tite being used to prevent slippage in the past. I've used a small dab of lock-tite before but never rosin.

 

[RFears]

Yup, mine is sliding, about 100th so far. Accuracy hasnt been affected as of yet, so i am not doing anything till after hunting season. But it is sliding forward per recoil of the rifle......

 

[esshup]

I've had one slide aft on a rifle, without a brake; twice! It was a spring air rifle....

I was hesitant to say anything about the locktite, but I've used it as well. The downside is that it's a pain to remove off of the scope if you ever have to re-mount the scope and the rings aren't in the exact same place. It cured my problem tho. I used the blue locktite, and let it set up for 48 hrs. before shooting the gun.

 

[jimbires]

I had my scope move forward . I lightly painted the inside of the rings with clear fingernail polish . it seems to work fine . I'm guessing that polish remover will take it off if I remove the scope . Jim

 

[BMcKell]

Red loctite will put an end to that problem. To remove it, spray carburator cleaner on a rag and the loctite will wipe off and doesn't remove the finish from the scope. I had this problem with Burris extremes on a 300 ultra.

 

[canuck4570]

[/IMG]
put this on these are from NEAR MFG in Alberta Canada
the rifle is a 450 Marlin and the recoil is around 45 pounds and no slippage
screws are at 17 inche pounds only.....
they are made of titanium alloy
stronger than steel and much lighter