Tips for scope mounting (for heavy recoil)

[Njal Thorgeirsson]

Hello,

I have attempted to mount a Nikon African scope on my Ruger No. 1 in .458 Lott.

Knowing the rifle is a heavy kicker (and that Ruger dovetail rings don't generally align all that well), I chose to purchase a lapping kit (wheeler engineering). I thoroughly lapped the rings, checked alignment and carefully mounted the scope. I applied moderate torque to the 8 screws (with blue loctite).

This morning I took my rifle out, and 3 rounds later, the scope had moved forward (Yes, forward) about 4 mm.

What can I do to keep my scope settled? Do I need to borrow a torque screwdriver from a friend to ensure they are sufficiently tight? Do I need to put some electrical tape on the rings to keep it settled? Is there some adhesive-like substance I can put between the rings and the scope?

FYI this happened with only moderate loads (350 grains @ 2450 FPS)

 

[rodinal220]

I use the liquid electrical coating from 3M.There are other similar products if you cannot locate this one in your local electrical supply/hardware store. Just clean and degrease the inside of the rings and apply a thin coating,allow to dry thoroughly and then mount your scope.

http://www.3m.com/product/information/Scotchkote-Electrical-Coating.html

 

[Njal Thorgeirsson]

That's an interesting one! I'll wait for a few more replies but that certainly seems like a plausible idea. I don't think tape will work because (after lapping) the rings fit too tight to the scope. A thin coat of something (like that 3m electrical stuff) would be optimal!

 

[rodinal220]

I wouldn't use tape,the adhesive will degrade in time and it will slip. I learned this technique from an old article published by Ross Seyfried on how to mount scopes for just your application. All my scopes get this regardless of recoil level.

 

[primalmu]

Define "moderate torque."

 

[chaser_2332]

have the receiver drilled and tapped for a regular picatinny base and use some high quality rings of your choice.

 

[Geno]

Lap the rings, apply Loc Tite to the ring interior, place the scope in the rings, torque to specification.

Geno

 

[Njal Thorgeirsson]

Define "moderate torque."

"moderate torque" is hand-tightening the screws with a screwdriver that has a small-diameter handle. I didn't absolutely torque them as tight as possible, but I tightened them as much as possible without re-positioning my tightening hand (if that makes any sense).

I am not going to remove the existing base because I like the option of the open sights if I remove the scope, and I don't really want to modify the firearm (nor do I have the spare cash to have a gunsmith do it or to buy high-quality rings and base). Additionally, I don't see what "high quality rings" would do besides making the lapping job easier. Contact with the rings should be nearly 100% if lapping is done properly. (Correct me if I'm wrong).

I think I like the idea of loctite on the rings as well (although I'd be a bit afraid that the scope would stick to the bases, should I ever wish to remove it).

EDIT: Does anyone have a good description of how tight those screws should be? I may have a friend who has a torque screwdriver, but I do not. I assume irreversible damage to a scope can be caused by over-tightened screws.

 

[MCMXI]

Njal Thorgeirsson, you seem to be surprised that the scope moved forward under recoil. This is the typical way a scope will move if there isn't enough friction between the rings and scope tube. I'm not familiar with the Nikon African but a common trick with scopes on rifles with lots of recoil is to move the scope forward until the ocular bell housing makes contact with the back of the rear ring. I think it's D'Arcy Echols who machines a conical taper into the back of the rear ring for this very reason.

If your rings are properly lapped you shouldn't need more than 15 to 18 in-lb on the ring screws.

 

[Njal Thorgeirsson]

Njal Thorgeirsson, you seem to be surprised that the scope moved forward under recoil. This is the typical way a scope will move if there isn't enough friction between the rings and scope tube. I'm not familiar with the Nikon African but a common trick with scopes on rifles with lots of recoil is to move the scope forward until the ocular bell housing makes contact with the back of the rear ring. I think it's D'Arcy Echols who machines a conical taper into the back of the rear ring for this very reason.

If your rings are properly lapped you shouldn't need more than 15 to 18 in-lb on the ring screws.

Yes, I was surprised! This is the first time I've had a scope on a firearm. Actually, the bell housing is about 1/3" from the rear ring, so I could certainly move the scope back 1/3". I added a little extra eye relief because I figured it was better to err the other direction, to increase rigidity and reduce flex in the tube behind the rear ring.

EDIT: Oops, went the wrong direction there. I'd have to move the scope forward by over an inch to hit the bell housing on the front ring. Unfortunately that won't be an option. Thanks for the exact figures; I'll see if I can track down a torque screwdriver.

 

[MCMXI]

Actually, the bell housing is about 1/3" from the rear ring, so I could certainly move the scope back 1/3". I added a little extra eye relief because I figured it was better to err the other direction

Let's make sure we're on the same page here. I'm suggesting that you move the scope AWAY from you so that the ocular (rear lens) bell housing makes contact with the back of the rear ring (nearest to stock). This will prevent the scope from moving forward under recoil. As I mentioned, this is a common problem with heavier DG scopes on rifles chambered for powerful cartridges and this is one solution that has been proven to work well.

 

[eastbank]

i had a very light(i mean very light) 358 norma mag. built on a 400 surprime mauser commrersial action in the 70,s and after losing several scopes and movment i put a 3x leupold scope on it with custom made dual dove tail bases and rings and put fine valve grounding compond on both insides of the rings and it held the scope with out any forward movment and the leupold keep its guts where they were to be. today you can buy dual dove tail rings and bases from leupold and i think burris. eastbank.

 

[Uncle Mike]

Loc-Tite the scope tube in the bottom half of the rings.
And IF you reamed your rings too much...get new rings, re-do.

 

[primalmu]

Personally, I think I would have purchased a torque screwdriver long before a scope ring lapping kit. My torque screwdriver has been indispensable, and one of my more valuable gun-related tools.