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Ring slippage

 
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  #15  
Old 12-30-2009, 01:56 PM
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Join Date: May 2007
Location: California
Posts: 458
Re: Ring slippage

A technique I learned years ago: Paint the (inside) of the lapped rings with a dilute solution of 3M Electrakote Electrical Coating.

Dilute a dollop to proper viscosity with acetone in a shotglass, paint on (lapped) rings, let dry a bit, apply scope, torque rings...effects a solid bond between scope and rings when completely dry, but is easily removed with a little heat and cleans up with acetone. Will not harm scope finish.
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  #16  
Old 12-30-2009, 10:55 PM
GNERGY
 
Posts: n/a
Re: Ring slippage

I use a product called stik n seal on the inside of the rings. Once it is dry you just scrape off the excess with your fingernail or a toothpick. If you ever have to remove your scope it just comes off with your fingernail.
You could also use black RTV silicone sealer.
You just need something with a good shear strength.
Tarey
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  #17  
Old 12-31-2009, 09:59 PM
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Join Date: Dec 2001
Location: Mukilteo, WA
Posts: 1,091
Re: Ring slippage

I am of the opinion that if you need any sort of goop, glue, tape or the like between the rings and the scope you'd be better served by figuring out why they don't fit or upgrading to rings that are adequate for the job at hand.

Shear strength is right. Most silicone sealers, various tapes, etc, have less than 100 psi shear strength. With only 2-3 square inches of effective contact you're talking a couple hundred lbs of force required to fail. That's not much. Many adhesives (epoxy-like) can offer a couple thousand psi. That's what the glue's strength is rated for itself, its adhesion to your scope and rings being anywhere near that strong is not assured. So unless you're literally gluing them together with something equivalent to bedding compounds for a near permanent bond (rediculous, unnecessary overkill IMHO), you're likely doing more harm than good as softer substances will be compressed, ooze out and reduce the clamp load of the rings on the scope.

8 properly torqued ring screws offer over 5000 lbs of clamping force. The cf of various types of aluminum on aluminum is typically well over 1 which means well more than 5000 lbs being required to move the scope. Now that's bare, anodizing can reduce the cf but as you can see even when reduced significantly you're still talking several thousand pounds of holding force.

Where I believe many go wrong:

Over lapping such that the rings halves contact each other and don't clamp the scope. This is easy to do with some brands, impossible with others.

Lappping so "well" the rings are literally polished to a very smooth finish. This will lower the cf. You might actually want to rough them up a bit.

Screw torque being incorrect for various reasons. The screws and the holes should be very clean. Many use locktite which after using on the rings a few times can lead to a bunch of buildup that gives false torque readings. I suggest clean screws and holes with a drop of oil on the screws.

Upgrading to rings that use 8-32 screws can be helpful as they'll better handle an increase in torque if you desire. If you're torquing 6-32 screws much more than 20 in-lbs and they aren't grade 8 you're they are likely yielding and losing their clamp load on the scope.

Upgrading to 6 screw rings for sever applications is a much better way to ensure no movement than trying to glue stuff together.

Another tip--while it's impossible to know the exact finish every company uses on their scopes so it's impossible to get exact cf numbers for everything, but typically aluminum will have a higher cf against such coatings than steel. So, especially if you lap your rings you might find aluminum rings hold the scope better than steel.

Hopefully that helps.
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  #18  
Old 01-01-2010, 10:45 PM
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Join Date: Aug 2002
Location: Southern Illinois
Posts: 241
Re: Ring slippage

I'd go easy on the Rosin and the torque. Almost every set of rings I've seen recommend 15 in/lb of torque. You had yours tightened "farmer tight," a term coined by John Barsness. I think the only reason you didn't damage the scope tube was you lapped the rings. Even so, I think a lesser scope tube would have been crushed.

Last edited by Magnumdude; 01-01-2010 at 10:51 PM.
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  #19  
Old 12-26-2010, 04:01 PM
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Join Date: Nov 2009
Posts: 804
Re: Ring slippage

There are only a few likely causes for your problem. From an engineering standpoint, I do not believe you have the tension you think you have if you did the scope should never have moved. Based on that premise, the things to check:

Rings are contacting each other. You said no, but some rings have an area right around the screw that sticks out slightly.

Screws are bottomed out in holes. This shouldn't be possible, but it the tap wasn't run in far enough it could be an issue.

Rings were lapped too large for the size of the scope so there isn't uniform pressure on all sides of the scope.

Rings do not have adequate surface area to hold the scope. There is a reason many 50 BMGs have 3 or even 4 sets of rings!

If you have checked these things there are several possible fixes:
Use Locktite. It works. Use 1 drop on top & bottom of each ring.
Use a balloon, yes a balloon! Stretch balloon rubber around scope & mount in the rings. A balloon is stretchable to less than .002 & this gives a rubber traction gasket that will hold almost any scope. (Gunsmith showed me that 40 years ago when mounting a scope on a 12 gauge & it worked well!)
*Add a third, or fourth, or fifth ... ring. (Be sure they are lapped after mounting on rifle as this is super critical when more than 2 rings are used.)
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  #20  
Old 12-26-2010, 06:08 PM
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Join Date: Nov 2005
Location: Texas
Posts: 1,844
Re: Ring slippage

Just about the entire BR crowd uses Aluminum myself included for both competition rifles and sporters. JJ Loh makes them from 7075 in the T7 condition (Kelby Style). I also bond my bases as well and they are 2pc because my actions are stiff enough to preclude the use of 1pc bases.

I have (Sinclair has them) used these double screw rings on lighter, more powerful non braked rifles with heavier scopes that you are discussing here. Never had one slip or move on me ever.
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