Scope mount lapping?

I'm planning on buying a nikon P223 scope for my AR and will be buying the nikon p mounts that are designed for it as well. Do you guys think it's necessary to get the mounts lapped?

From what I've heard from experienced smiths and what I've ovserved personally there is not real reason to lap the aluminum mounts as they are quite precise already. I would just mount it and rock and roll. And as you mentioned they are intended to be paired so I'd think it'd be as good as it could be. My .02. I'm sure others will disagree but as is life.

How many 1000yard shots do you intend to do with this gun ? Are you going to lap the rail as well that you screw the mount to ?

traveller said:

How many 1000yard shots do you intend to do with this gun ? Are you going to lap the rail as well that you screw the mount to ?

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I'm not very rifle savy, it's just something I learned about watching youtube videos on gunsmithing from midway usa so I was curious if it's necessary to properly mount a scope. But to answer your question, none. It's just a 3x magnification. lol.

Lapping, bedding, grinding, and polishing are really only necessary in the long range precision game.
Heres some questions for you.
Is the barrel free floated?
Is the barrel a match grade barrel from a reputable manufacturer?
Are you running 77 grain reloads at long (400+ yards) in competition?
Are you shooting off of a bipod, shooting sticks, or some other rifle rest?
Are you using a high quality/high magnification scope?

If you answered "no" to the majority of those questions then dont worry about lapping the rings.

mopar92 said:

Lapping, bedding, grinding, and polishing are really only necessary in the long range precision game.
Heres some questions for you.
Is the barrel free floated?
Is the barrel a match grade barrel from a reputable manufacturer?
Are you running 77 grain reloads at long (400+ yards) in competition?
Are you shooting off of a bipod, shooting sticks, or some other rifle rest?
Are you using a high quality/high magnification scope?

If you answered "no" to the majority of those questions then dont worry about lapping the rings.

Click to expand...

Cool, thanks for the info!

Not even in the precision long range game.

You buy QUALITY rings, and lapping is not required.

You bed the mount, so that the mount is not bent of twisted, so no lapping required.

And if you lap aluminum rings, you remove the anodizing leading to wear and corrosion.

The rifle receiver is not perfect, at least not on top where the base attaches.

The screw holes in the top of the receiver are not always in perfect alignment with the receiver axis. The base may not be perfect, both in the overall manufacturing precision and in the way it fits the rifle.

Most rifles will cause the base to twist (like stripes on a barber's pole) as it is tightened down. Once we insert error into the system, it contributes to all other errors. This twist telegraphs all the way through the system.

Rings are not perfect, despite the "CNC machined on modern machinery to close tolerances". News flash: They are ALL CNC machined - it's how parts are made these days, junk parts, good parts, well designed parts, design errors....without CNC tooling, parts cannot be produced fast enough to make any money. What they sell for matters far less than one might imagine.

Cutters are not perfect and can chip and dull. As cutters dull, they deflect metal (vs clean removal) and raise burrs. A perfectly guided CNC cutter will follow its designated path, but if the cutter is not perfectly sharp, it will leave incomplete cuts and undersized openings, and at edges of the cut, burrs will be raised. This applies to the inner surfaces of the rings, that contact your scope, as much as it applies to every machined surface.

All of these errors and flaws come together to support and secure your scope and any/all of the above errors will affect the way the scope is mounted.

Lapping rings is not just for long range and it's not just for precision, it is to provide the best possible interface between the scope and the rings. Good mounting provides very secure mounting without causing damage like dents, scratches and 'ring marks'.

A hard recoiling hunting rifle benefits by the additional surface area and better grip every bit as much as a hardened sniper rifle or precision match gun.

Got a cheap scope, cheap mounts on a basic rifle? Don't bother, just tighten hell out of everything and the mounting job will probably not be the weak link.

Got a nice scope in solid rings, just bolting everything together without regard to fit, finish and alignment and you can knock a few hundred off the value of your new glass via ring damage and bent tubing. Adjustments bind and warranties are null. NightForce specifically disallows warranty coverage of damage due to bad ring fit.

Bases do not get lapped.

Ideally, bases are epoxy bedded to the rifle receiver, which provides 100% contact with both parts and allows the base to lie flat and straight. Bedding the base is positively the best way to get around this fit issue.

If epoxy bedding is not available, for reasons such as time constraints or lack of shop facilities, bases can be shimmed to eliminate a lot of the distortion caused by incorrect fit/alignment. I often find the need to use 0.001" to 0.005" shims on new Remington and Savage actions using Badger and similar quality bases.

Once the base is as straight as we can make it, ring alignment is better, but even perfectly aligned rings can have high spots and burrs on the clamping surface.

By taking every opportunity to improve alignment and fit, we help keep the scope toward the center of its adjustments, providing both maximum travel and stable performance.

Lapping removes these sharp spots, high spots and burrs, promoting better alignment and more complete contact surface. If I were putting a $300 scope on a $500 rifle with $50 rings, I'd be less inclined to lap than I would with a $2,500 scope in $170 rings on a $3000 rifle, but I'd probably still do it for the enhanced solidity.

Again, it is popular to assume all of the high dollar parts turned out on exalted CNC machinery is perfect, or at least close enough not to require additional attention, but that is a huge fallacy.

Iron Brigade Armory, the guys who built rifles for Blackwater and Chandler, put together one of mine and almost ruined the NightForce scope by forcing it into Badger rings that were badly machined. The scope could not even bottom out in the rings and the entire source of contact was where the edges of the rings bit through the anodized scope surface. FIVE MINUTES with a lapping bar and a modicum of adult supervision would have prevented this damage and provided the proper mounting job that was lacking due to the user's ASSumption that all rings are perfect, especially name brand crap.

The down side of lapping is that overdoing it can ruin a set of rings and if they become loose enough that the scope moves, scope damage may also result. Lapping, correctly done, does not take out a lot of material. We are not re-machining the parts, we seek only to remove burrs and improve contact. As with any precision work, care must be taken and thought given to the task at hand.

I practice what Ed just preached with my $2500 scopes in $200 rings on $5500 rifles. It works for me. I had one setup that I really did not like and I lapped the hell out of those rings before I was happy. I think someone went a little bit crazy with the coating on that set. I just recently pulled a scope off a .308 at 792 shots and after rubbing the scope tube with my thumb for a minute, you could hardly tell it was ever in a set of rings.

5 shots-



Torque them down in an alignment bar and lap 'em.

Scope ring lapping may make a difference. So will barrel floating, glass bedding, precision reloading, barrel lapping, etc. but most of these differences are undetectable because the average shooters abilities make a much bigger difference. If you are mounting the best scopes with the best rings and mounts on the best rifles go ahead and lap but make certain your lapping equipment is also precision ground and matched to the exact dimensions of your scope and mounting system. Anything else just makes well lined up set of mounts that are not the perfect size which will cause stress points.