Barrett M99 scope slipping forwards

[omt223]

I have a M99 in 50 BMG with an Arken SH4 34mm tube. EGW couldnt give me an answer if their keystone rings were up to standard for 50 BMG so they sent me a set in exchange for a review. The arken rings that were "rated for 50" cracked.
Using the torque EGW gave me (15 in-lb) the scope slipped forwards about 1cm after 20 rounds or so. To me, the scope in the rings is SUPER slick compared to most rings I have ever messed with (with the rifle on the bipod and the lower half of the rings only, the scope will slip all the way back to the bell).

They told me I can tighten the screws to 30 in-lb max but that damage to the scope may result. Also stated that a slip of computer paper lining the rings may also provide more surface area.

Any other ideas on what I can do to remedy this without buying a lapping bar?

 

[shootallday]

Maybe crosshatch the rings with some large grip sand paper.
I had a old steel tube scope that would always slip with the aluminum rings so I put some blue locktite on the rings, jencky but it did work and was not to hard to remove the rings from the scope when it was replaced. Could use some rossin as well.

 

[Wolf76]

Sounds like some friction is needed. What about rubber cement / loctite / similar product to add some grip? Roughing the rings up prior to adding some compound also makes sense. I've used electrical tape on my 12 ga slug gun w/scope setup with success as well. Haven't shot the 50, but slugs are not for the recoil sensitive.

 

[BillLarson]

Use 3 rings.with rosin.

 

[omt223]

Sounds like some friction is needed. What about rubber cement / loctite / similar product to add some grip? Roughing the rings up prior to adding some compound also makes sense. I've used electrical tape on my 12 ga slug gun w/scope setup with success as well. Haven't shot the 50, but slugs are not for the recoil sensitive.

The recoil is really not bad to me; certainly comparable to other high power rifles like a 30-06 hunting rifle with a lot more concussion

 

[Bravo 4]

Use 3 rings.

Yep, or even 4.

 

[Shane Lindsey]

The brake is probably what is causing the slippage. Normal recoil is straight back. With a brake it is straight back and then sudden stop in the opposite direction.

 

[308plinkerVT]

I do believe there is a green loctite specifically for this type of circumstance. A little roughing of the surface may or may not help, technically are "removing" friction surface as well with that sandpaper. I personally would try that after fully de-greasing and the green loctite.

 

[Ken61]

Why not different rings? These don't seem up to the job.

 

[Arkansasdad]

I have a M99 in 50 BMG with an Arken SH4 34mm tube. EGW couldnt give me an answer if their keystone rings were up to standard for 50 BMG so they sent me a set in exchange for a review. The arken rings that were "rated for 50" cracked.
Using the torque EGW gave me (15 in-lb) the scope slipped forwards about 1cm after 20 rounds or so. To me, the scope in the rings is SUPER slick compared to most rings I have ever messed with (with the rifle on the bipod and the lower half of the rings only, the scope will slip all the way back to the bell).

They told me I can tighten the screws to 30 in-lb max but that damage to the scope may result. Also stated that a slip of computer paper lining the rings may also provide more surface area.

Any other ideas on what I can do to remedy this without buying a lapping bar?

Order a set of "Near Manufacturing" rings and bases out of Canada. They wont give up anything. I use the three ring set up designed for the Barrett. No slip, no problems, I have probably owned a few hundred sets of mounts and rings and none can come close to these. Happy shooting.

 

[skipglo]

Order a set of "Near Manufacturing" rings and bases out of Canada. They wont give up anything. I use the three ring set up designed for the Barrett. No slip, no problems, I have probably owned a few hundred sets of mounts and rings and none can come close to these. Happy shooting.

Correct you are!

 

[del2les]

As stated above, I have used rosin, powdered sugar, double sided Scotch tape, abraded the inside of the rings, etc with good results on heavy recoilers. Sometimes, even the usage of 3 rings did not completely stop the slippage and additional measures were needed.

 

[skipglo]

I have a M99 in 50 BMG with an Arken SH4 34mm tube. EGW couldnt give me an answer if their keystone rings were up to standard for 50 BMG so they sent me a set in exchange for a review. The arken rings that were "rated for 50" cracked.
Using the torque EGW gave me (15 in-lb) the scope slipped forwards about 1cm after 20 rounds or so. To me, the scope in the rings is SUPER slick compared to most rings I have ever messed with (with the rifle on the bipod and the lower half of the rings only, the scope will slip all the way back to the bell).

They told me I can tighten the screws to 30 in-lb max but that damage to the scope may result. Also stated that a slip of computer paper lining the rings may also provide more surface area.

Any other ideas on what I can do to remedy this without buying a lapping bar?

Loctite, 3 rings, But don't OVER TORQUE the rings...you can crush the internals...one of the first signs of over torque is the parallax gets stiff...next sign....well...it's a good it's not an expensive scope!!!! Good luck....50s are a ton of fun...but definitely present new challenges!.....One other thing..my scope is torqued to 24 inch pounds. .I always check torque before shooting and about every 10 rds....scopes were never designed for FORWARD PULL created by muzzle breaks so they present new challenges to the manufacturers!

 

[Shane Lindsey]

We never had issues with the M82s. Not sure what those rings were, but they were nothing like these today.