View Full Version : Lap scope mounts or not??
May 19, 2011, 06:14 PM
I've shot for years, but have never mounted a scope. I'm mounting a Vortex Viper 2 x 7 variable on a Savage 24V. I've read that one should not have a lot of correction to do to zero a scope. If so, shimming needs to be done. (?)
The gun is .222 Remmington over 20 gauge. Using a chamber adapter to .22 rimfire, shooting out back (I haven't had a chance to get to the range yet to try the .222.) The bullets are keyholing due to a problem with the adapter, but are pretty consistently hitting about 15" low. I'm assuming the .222 will hit similarly. (?) (I called Ace in Alaska...the keyholing may be fixed by using 40 grain, lead only bullets, cleaning all copper fouling, and chamfering the chamber adapter...so I'll be trying that.)
Anyway, just how much adjustment is okay to do to a scope? Should I shim the rear mount up to get it closer to where the scope is at it's natural zero, (or whatever you call it).
Thanks for the help before...I did decide to go with see-through rings, as compromised as that is. The JB Holden Ironsighter's sit very low and allow use of the original sights. BUT, I had to take a dremel tool and create relief for the back mount to allow the gun to close. These mounts say they fit the Savage 24-V, but not so, without modification.
May 20, 2011, 10:53 PM
first, i think you will get rid of the keyholing and find much better accuracy tossing the .22LR adaptor and using 222.
Correct way to mount a scope.--
1. Center the crosshairs- Crank the windage on the scope all the way to the left(don't force it too far). Turn it all the way to the right now counting the clicks or turns if the scope doesn't have clicks. Turn back left half the counted clicks(center). use the same technique on the vertical adjustment.
2. Install mounts and rings. Looks like you are probably using clamp on type. Evenly tighten mounting screws. Mount rings in bases. For Redfield twist on, put a wooden dowel in ring and twist into position. Now you really need steel ring levels(1" steel bars pointed on one end) these are clamped into the rings with the pointed ends pointing at each other in between the sets of rings. If they are not pointing perfectly at each other that indicates either misalignment needing alignment modifications through twisting the rings to point at each other(rough horizontal tuning). If the points indicate that your horizontal is still off or one ring is higher than the other, then you need to lapp accordingly to make your rings match and the pointed indicators to indicate equal rings. As far as schimming, I have used aluminum foil and strips of beer cans with success (on other peoples' cheap .22's). In my opinion, if you are so far off that you need to shim, something else needs to be done to fix the problem.
These rough guidelines will work for cheap aluminum see through rings too, you just don't have a lot of adjustment and many of these cheap type mounts are so out of spec they should be tossed. What you are trying to do in any case, is get the front and rear ring to support the scope tube evenly and completely straight.
Mount scope, tightening screws evenly, and bore sight. Hopefully, with perfectly symmetrical rings and a centered scope, you won't be far off.
Sorry for the long post that wasn't really even what the OP asked for. Thought it was about scope mounting and possible lapping, until I looked back and saw it was about shimming. Oh well
May 21, 2011, 04:04 AM
I'm an ex gunsmith. Fitted lots of scopes. I confirm Publius's instruction that the first move is to centre the reticle by adjusting fully one way, fully the other, then halfway back. Same for verticle. That's necessary because you need adequate left/right and up/down adjustment after everything is tightened up. Actually, its all left/right, the up/down is much less important because it is in the lateral plane that most errors in the mounts occur.
As publius says, take it easy when you get near the extreme left or right adjustment. Most scopes have clicks, and get noticeably tighter near the limits of their adjustment. Stop when you feel it getting stiffer, don't push it. Also be aware that some scopes don't have click adjustments. Leupold is a smooth movement without clicks, and comes to a dead stop at the end.
Now, here's where it gets interesting. Scope rings are never, and I mean NEVER, properly aligned unless they have been lapped in position. That's because of normal tolerances in the manufacture of rifles and bases and rings. I never saw any that were not out to some extent. The result is that the ring grips the scope by its edges, and no matter how tight you cinch them up, there is not enough grip with that point contact to prevent the scope from shifting in recoil.
When the scope shifts the ring can scrape the finish off the scope, and I have seen expensive scopes that were badly disfigured in that way. I've even seen scopes that were slightly dented by their rings.
What you want is rings that grip the scope tube exactly and evenly over the whole inner surface of the ring. You can only get that if they are exactly aligned, and you can only get that by lapping them. You need a precision machined rod about twelve inches long. For a one inch tube scope that's a one inch rod. Apply lapping compound, 600 grit is about right, and lap the rings back and forth. You can see when the job is done because it progressively removes the blue as it cuts.
I have a simpler method that is theoretically less precise but works well. I machine a rod 24.80m dia. I wrap a single thickness of wet or dry around it, which brings it to 25.40mm (one inch) and polish the rings with it. I start with 180 or 220 grit for rapid metal removal, and finish with 320. An finally, a coat of cold blue. I assure you that, when the scope is dropped in, that bank vault-like feel of 100% solid fit can be felt. I have set up some heavy recoiling rifles this way and never had one come back.
How far out are the rings, typically ? One to three thousandths, as close as I could tell because it is not easy to measure. Six thou in the worst cases. But that's all it takes for there to be nothing more than point contact at the edge of the ring, and effectively no grip.
Even today, despite the absolute proof that rings are always out, and the necessity for this procedure, it is done only by a tiny minority of gunsmiths or dealers. Why ? I found that it is not believed until I prove it in front of their eyes.
Which brings me neatly to the pointed test rods. Forget them. As Publius says, if the points don't line up you know you have misalignment. But they don't tell you how much or which way. If they don't line up left/right, it doesn't tell you whether one ring is left and one right, or whether they are out left or right by different amounts. And if the points do line up, both rings could be out in the same direction by an equal amount. My argument is that the ringswill ALWAYS be out, without exception, so why bother with test devices that don't tell you anything, just lap 'em as a matter of routine, because you'll always have to.
I made my own test bars, because they are useful for just one thing, showing the customers who just don't believe it until they see it.
Shimming is another matter. Shouldn't be necessary unless the bases or rings are not right for the rifle. But it is a legitimate way of getting the bases more or less right, and I have to concede that some military rifles like the ubiquitous M98 can have enough variance in receiver height to require shims. You can buy them from Brownells, but most gunsmiths keep some shimstock, and I used to cut my own.
Just to further illustrate, for the sake of interest, the sort of thing that gunsmiths encounter, I had two rifles with Weaver bases and rings, that would not shoot to point of aim at max lateral scope adjustment. As you know, Weaver mounts do not permit lateral adjustment. One rifle was corrected by reversing front and back rings, the other by turning the rings 180 degrees. That tells us that some things are fixed by simple methods, and that manufacturing tolerances can make that much difference.
May 21, 2011, 07:39 AM
No such thing as an "ex-gunsmith"----you may be officially inactive, but you still have a wealth of knowledge & life experiences to share with the readers of this forum. Ooooo-rah !!!!!!!
SERIOUSLY, MR. DIKKO IS CORRECT IN HIS PERSONAL & PROFESSIONAL ASSESSMENT OF SCOPE MOUNTING PROBLEMS HE HAS WITNESSED & CORRECTED. SINCE THE EARLY 1980'S, I HAVE MOUNTED AT LEAST 25 SCOPES FOR FAMILY MEMBERS. EVERY RIFLE WAS EQUIPPED WITH EITHER LEUPOLD / BURRIS DUAL DOVETAIL MOUNTS AND RESPECTIVE SOLID STEEL RINGS. EVERY SCOPE WAS MOUNTED AS LOW TO THE RECEIVER AS THE EYEPIECE, OBJECTIVE, & OPERATIONAL CONTROLS WOULD PERMIT. RIFLES WERE B/A, PUMPS, AUTOS, OR LEVER ACTIONS.
EVERY PAIR OF RINGS WERE FIRST ALIGNED WITH A 1" DIAMETER SOLID STEEL SINCLAIR LAPPING BAR. THEN THE RINGS WERE LAPPED WITH VERY FINE NON-EMBEDDING LAPPING COMPOUND, UNTIL ABOUT 80% OF THE BLUE WAS REMOVED INSIDE THE RINGS. I ALSO CAN ATTEST TO MR. DIKKO'S STATEMENT OF THE SCOPE MATING WITH THE RINGS WITH THAT "BANK VAULT" FEELING OF SOLIDARITY----NEVER HAD A COMPLAINT OR MENTION OF A PROBLEM FROM ANYONE !!!!!!!
I WANT TO PUBLICALLY THANK THE BENCHREST SHOOTERS WHO SHARED THESE TECHNIQUES WITH ME SO MANY YEARS AGO. I SIMPLY APPLIED WHAT I LEARNED TO SPORTER RIFLES TYPICALLY USED IN HUNTING SITUATIONS.
SCOPES WERE ALWAYS OF HIGH QUALITY (BURRIS, LEUPOLD, ZEISS, OR HIGH END SIMMONS).
ANYHOW, THIS SYSTEM HAS ALWAYS WORKED FOR ME & I SHALL NEVER DEVIATE FROM MY PROVEN PROCEDURES.
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