Would you recommend lapping the rings?

[tpcollins]

I have a DNZ 1 piece mount on a Savage Model 12 converted to a 450BM, and I want to shim the rear pad with a .012" shim so eventually I can get more elevation/yardage on the Leupold CDS turret.

Wheeler makes a stone tool to put in the rings to lap them so the rings are straight. I have tube that's just under 1" and I could wrap some 400 grit emery cloth and perhaps accomplish the same task.

Good idea or is the .012" shim not going to matter? The DNZ's mounting pads are each 1 3/8" long and about 3 1/8" spacing in between. Thanks.

[HiBC]

I'mnot much of a shim guy. I might look for a 15 or 20MOA sloped base.
If you start with a base that fits the rifle full contact,a shim gives you two lines if contact.The rest is lifted off the receiver.And the screws are reaching across a gap.
If the screws pull the base down,two bad things. Most of the strength of the screw is used up bending the base.And the base is distorted.So the rings will point in different directions. Maybe lapping is a workaround...till you re-tighten the screws.

First,I like my bases to match fit the receiver with no strain. I want both ends to Prussia blue transfer. With that sound foundation,yes,properly lapped rings are a great idea.
With two piece bases,I use a surface plate and indicator to assure the bases are the same height to under .001. I re-machine them as necessary

If your scope is made to tolerances in the tenths of thousandths...and if any adhesives or sealants are used,distorting the tube as the ring screws are white knuckled down can undo what you paid for.

But I don't think tubing and 400 grit sandpaper are the path.

The lapping rods are available. I'll tell you how I do it.
I worked at a place that had Swiss Turning Machines.The stock for those comes precision OD ground .005 under nominal..The 1 in stock was .995.I scrounged some bar ends in 1 in and 30 mm.also .005 undersize.

The size of the rocks in your lapping grit plays a part in the size your lapping rod will cut. In theory,400 grit is.0025 rocks. 320 grit is .003125 rocks.
Add that to the .995 rod and you get real close to 1.000. Generally,the grit embeds to a degree in the (hopefully) softer lapping rod. I'd go with the 320.

I'm first concerned with the saddles. I lap them on the base open. Put asubtle match mark on the caps so they always go the same way. I'll knock high spots off just stroking on the rod.
Then lap assembled a bit.You will see a lot as the blue is cut off the rings.

At maybe 80 or 90% I'm satisfied the tube won't distort.

[OzeanJaeger]

X2 on all that.

Brownells has a good video that demonstrates everything HiBC just said about lapping scope rings for a precise fit. Really, many pros are leaving rings altogether and going for the milled, one piece units that make maximum contact with the rails.

The only thing I can add is that you can also bed your rings. They’ll be just as perfect as lapping them, and you don’t need to buy anything (if you’ve already got 5min epoxy). You can paste release wax right onto your scope tube and the ears of the rings and then run a thin layer of epoxy on the rounded part. Attach the scope exactly like you would setting it up except don’t Loctite the screws or put them in to full torque. About half will do it. Let it set up, take it apart, trim any excess, and your rings will also be trued.

I have done this on one scope just to try it and it worked perfectly. That said, I have a ring lapping kit, and I’m expecting a scope in about a week, and I’m going to lap those rings.

[tobnpr]

Don't shim a ring base. That results in misalignment, lack of full contact (impossible to "lap out" that much misalignment and achieve near full contact), and possibly a damaged tube.

Get a down angle base if you need more elevation adjustment.

[tpcollins]

So putting a 012" shim under the rear mounting pad of this mount will compromise my scope?

[HiBC]

I can't say for sure if the small mounting screws with fine threads will distort your base much but people who work with optics...telescopes and microscopes,are quite concerned that the slightest clamping pressure to mount the glass will distort it.

You can do what you want. There may be some bedding compound you can fill the gap with...and just snug the screws till its set. Then tighten them.I don't know what compound to recommend.Maybe a metallic or ceramic filled epoxy or Loctite product.I think Locktite makes a ceramic filled stripped thread repair.
I have never used it for anything. You might talk to a Loctite tech rep,or Brownells. You aren't the first and only!
Ihaveseen some brown stock bedding compound go gummy under a scope base..Maybe Hoppes or ? got to it.I suspect it was Micro-Bed.

Its my opinion you want the base to have full,solid,non-compessable contact between the base and receiver. You will get the most secure mounting that way,and you don't distort the base.

While you might want to verify it,If you CAN actually mount that ring/base without distorting it,that style of mount MIGHT be line bored or line honed straight and true...or it might be as cast or molded and need lapping.

Once again,I can't know what is there.Once the mount is set in place,screws tight,a light lapping will either show a high percentage cut,or high spots.

Folks see barrels,scope tubes,etc as solid. In fact,they are not.

I have come to believe a lot of scope adjustment repeatability issues I have experienced years ago MIGHT have been earlier technology,but then it might well have been my DIY scope mounting ....(anyone with a screwdriver can mount a scope?). I have seen some HORRIBLE scope bases from name brand outfits....and consider the headaches from Mil-Surp sporters!!!

I don't want to spend the big bucks on a quality scope and bend the tube .008

I would guess the tube is weakest at the turrets,and some internals might be set in a variant of superglue..which can pop.

You may not have access to any machining equiptment and you may have a limited budget. I respect that.

The way I would do what you want to do,is mic your tubular Savage receiver and precisely re-cut the bottom of your base on the slope I want to match.

Or I would buy a base /rings that is sloped.

With limited resources,I might try a shim with bedding. I would not use just a shim. Then I would lap.

[tobnpr]

^^^
My bad... I missed that it is a one piece base- I was referring to individual ring mounts.

That said, its still not a great arrangement, as you have a minimal clearance size hole for the screw shank in the mount. When you shim, you're angling the hole- while the screw needs to be perfectly vertical. It will bind in the hole (amount depending on the thickness of the shim), and won't have full contact with the base when torqued down.

IIRC, about .005/inch equates roughly to about 20 minutes. If the mount is rigid enough it might not flex enough to affect ring alignment. If you have a friend with/access to a mill the base can be machined to whatever angle you want.

[tpcollins]

A guy suggested to me to bed it with epoxy ( I like JB Weld ) and just put a narrow strip of the .012" stock behind the rear most screw, coat a release agent on the receiver and screws, rough up the underside of the 2 pads, screw in all 4 screws a few turns and then just snug up the front and rear screws only - wipe off the excess. That should put an even taper the entire length of the 2 mounting pads.

DNZ wanted $75 plus $10 shipping to machine an 8 MOA slope across the bottom. I'll go to ACE tomorrow and get some JB Weld for about $6.

[tobnpr]

Bedding is a good idea.
Def rough up the pads (I use a small file or dremel) to cut through the anodizing, as your friend advised the epoxy won't bond to it. Be sure to degrease the pads thoroughly before applying the epoxy.
Take a Q-tip with the release agent and get some inside the holes, and along the side edges of the base.
Keep an eye on the epoxy (I use the fast cure JB for this, takes only a few minutes), when it's partially cured it'll be simple to "peel" the excess from the edges. Good luck

[JeepHammer]

There are as many different ways to do this as there are people doing it, one or two might work correctly...
Most people 'AssUMe' and that's the mother of all mistakes!
(And you know how to break up the word 'AssUme', makes an *** of 'U' & 'Me')

Assume nothing, check everything.

I'm with HiBC, but I do things slightly different.
I jig, or at least use a fine wire from muzzle to back of receiver to check the rail screw holes were drilled centered, a bunch are not...

I'm a fan of bedding the rail to the receiver, but I don't remove finish as suggested.
No sense in screwing up finish, the idea of bedding is to get the rail perfectly fitting the receiver curve.
Once it hardens that job is done, rails are cheaper than refinishing the receiver, and since you are using screws to secure (not glueing it down) there is no point in scuffing the finish on the receiver.
You are only gap filling with bedding...

I'm not above silver soldering the rings to the rail. No screws or clamps to come loose.
And honestly, once a rail & rings are installed, how often do you actually remove them?)
Again, rings/rail cheaper than refinishing the action/receiver.

I lap (using lapping bar & lapping compound) to ensure the ring bores are true with each other.
Two tips here, as written before, witness mark your caps!
A punch or file mark on the side, one mark front, two marks rear, both cap & saddle.
This get the caps back on it's matching saddle, and gets the correct side of that cap so the lapped set match every time.
I use a file mark, simply because a stright up & down line lines the correct cap on the correct saddle, and turned the correct way.

The second is a torque wrench. 10 or 15 INCH Pounds means 10 or 15 INCH pounds, not a screwdriver or Allen wrench "Snugged" up which can EASILY FLATTEN OR OVAL THE TUBE.
I'll say that again, you CAN oval (crush) the tube with just finger pressure.

If you *Think* you can accurately determine finger pressure, then use your fingers and try to hold a scale perfectly still at any given weight...
Muscle force is the WORST possible way to have repeatable results.
Torque screwdrivers are cheap for this very purpose...

Just one more tip,
Two or more screws per side of caps. Single screw caps are failure waiting to happen...
When you install a screw, you are STRETCHING the shank of the screw, over torque will ruin the clamping power of the screw, while under torque will result in loose caps.
TWO screws each side share the load, and provide redundancy.
If it's worth doing correctly, no point it screwing up with single screw caps.

Everyone has a different way of doing this, but this is 40+ years of experience from a gunsmith, so take it for what you paid for it.

[Mobuck]

"I have a DNZ 1 piece mount "
Looking at the design, I'd say you're pretty much stuck with what the mount provides.
If you feel the need for more elevation, you probably need to look at a different ring/base combination.
As far as lapping the rings, if I paid $50-60 for a scope mount, I'd expect it to be usable as-is w/o additional fitting.

[Unclenick]

If you are going to resort to shims and epoxy, I agree with the idea you use them on the base and not the rings, then you don't have to worry about lapping. Rather than get into a lot of fitting issues or risking loose rings, raising the back end of the base makes more sense to me.

[tpcollins]

Bedding put a consistent taper from front to rear, works for me.

[hooligan1]

DNZ rings are made out of one piece of steel and machined true at the factory, there is no need to lap these rings as they are perfect already from factory.
Bedding one end or the other isnt horrible but take your time, go through the steps dry a few times....