Shimming a scope?

T

The Famous Grouse

New member
I don't know if this is a firearms topic or a scope topic or what. I've actually never had to do this before, but I was out on the range at the weekend and decided that my .22-250 was just a little too high at 100 as I'd like to be dead on at 200. So I went to bring it down a couple of clicks and, well, no clicks left. Uh-oh.

The scope is the old style Japan made Bushnell Elite 6x24.

I haven't had to do this before, but if I recall correctly, you can either use scope shim stock for about $10 a square inch from the fancy pants gunsmith supply shop, or use a doubled thickness of aluminum can with the edges smoothed on a wet stone after cutting to size.

Anyone use either method? How thick of a shim does one need to add to gain 1 inch of adjustment back at 100?

If my brain is working correctly, I'm assuming I want to shim under the REAR ring. Correct? Since I can't bring the adjustment down any more, I have to bring the rear down and then adjust the scope back upward, right?

Grouse
 
I believe you want to shim the front which will move your reticle up and will move the bullets impact down. Leupold sells little packets of shim, not sure on the price but pretty reasonable. 1 piece of shim should get you where you want to be.
 
Last edited:
If it's a one piece base, shim under whichever end needs it. But DO NOT ever shim a scope or one end of a two-piece ring set. Rings are just rigid tubes that clamp the scope. They don't bend, and they have to be on the same centerline. Shimming a ring puts them out of alignment. When that happens, the scope gets a kink. Your setup being out so much it's pretty screwed up anyway. Don't mess with bedding the rings and with that much don't even think about lapping them. Save yourself a lot of trouble, just get some Burris Signature rings and learn about how they work. Problem solved.
 
like previously said, never ever shim scope rings, shim only under the bases. what model of firearm is it that u are having trouble with, savage?
 
I have seen scopes run out of elevation lots of times but what would be the reason for not being able to go down to 100? Unless it is set up for really long range it should do 100 should it not?
 
I have a rem 700adl that I put a single layer of aluminum pop can (pepsi) under the the scope on the rear ring( leupold one piece base,leupold rings). Properly torqued the rings,shot it that way for several years with a Burris fulfield 2. Came across a new takeoff barrel,after barrel change shim was no longer needed. The original barrel chamber out of spec,so it seems the barrel was my setup problem. The single shim got me about 3 inches at 100 yards.
 
Originally Posted By: The Famous GrouseI don't know if this is a firearms topic or a scope topic or what. I've actually never had to do this before, but I was out on the range at the weekend and decided that my .22-250 was just a little too high at 100 as I'd like to be dead on at 200. So I went to bring it down a couple of clicks and, well, no clicks left. Uh-oh.

The scope is the old style Japan made Bushnell Elite 6x24.

I haven't had to do this before, but if I recall correctly, you can either use scope shim stock for about $10 a square inch from the fancy pants gunsmith supply shop, or use a doubled thickness of aluminum can with the edges smoothed on a wet stone after cutting to size.

Anyone use either method? How thick of a shim does one need to add to gain 1 inch of adjustment back at 100?

If my brain is working correctly, I'm assuming I want to shim under the REAR ring. Correct? Since I can't bring the adjustment down any more, I have to bring the rear down and then adjust the scope back upward, right?

Grouse





something very wrong here. if it was mine i would have to figure out what was wrong and fix it the right way. pop can shims and other [beeep] rigging fixes would not cut it for me.
 
Originally Posted By: tnshootistI have seen scopes run out of elevation lots of times but what would be the reason for not being able to go down to 100? Unless it is set up for really long range it should do 100 should it not?

Some receivers are not perfectly level is one. Some scope rings/base combinations can have tolerance stacking that tilts the scope up or down. The barrel may be pointed up at such an angle that your scope doesn't have the necessary movement. Justlike a guy might find one that points left or right and we use all the windage. Not a common problem at 100 as it would take a pretty good tilt. Or wit my luck it would be a combination of the two.

AS I said.. Burris

Greg
 
I had a buddy that had an issue like this when he put his scope on his 17 HMR. It would shoot good groups but bottomed out 3" high of the bull. All he did to fix it was broke everything loose, and put it back together. Turns out the rear ring somehow did not sit flush to the base base when he tightened it the first time. I have never seen it happen except for that time but could be it. I would say it is prolly not in your case since I assume you have been using the rifle for some time and the recoil would most likely knock it loose by now, but it don't cost anything to check. Just a suggestion. Good luck!

Shelton
 
Originally Posted By: tnshootistI have seen scopes run out of elevation lots of times but what would be the reason for not being able to go down to 100? Unless it is set up for really long range it should do 100 should it not?

It's not rare to have this sort of thing. Usually it's not nearly so bad as what the OP is experiencing. On an action with a flattened bridge, that part could have been polished down a bit too far. On my CZ527 the scope mounting pads aren't level with each other, one's about .009" lower than the other. Also barrels aren't always straight in the action, it might be tilted up or down or to the side. And it can happen with any make of gun. The tech at Burris once told me they get scopes sent in for repair that are fine, it's the the gun that's off. Years ago on a CZ 601/.22Mag the barrel was so out of alignment the scope wouldn't come close to zero at 50yds when bottomed out completely....just like the OP's situation. One fancy big name custom 10-22 barrel did the same thing, the shank was much too loose. After Mike Bellm sleeved it things were fine. Stuff like that shouldn't happen but it does. Most all of my rifles have Burris Signature scopes and probably 1/3-1/2 of them use offset inserts. Even with conventional rings this can be rectified with a shim under the base, only if it's a ONE PIECE base. But after measuring height of about a dozen ring sets and finding none matching exactly, some as far as .005-.006" different one to the other, I'd never use conventional rings again.
 
Appreciate all the feedback and yes it is a head scratcher as to what, exactly is the root cause.

I know the final fix is new rings, but to Shelton's point, I'd like to try to figure out what the cause is before trying to put out the fire by throwing money on it.

To complete the picture, the setup is a Weaver base with Weaver Quad Lock rings. So I can shim the base.

First thing I'm going to do is take Shelton's point and take everything apart and look for something that isn't right, put it all back together and see if somehow I messed up the setup. I'm pretty careful with the whole process, but then again I once put a carb back together and got everything right except that I forgot to include the float, so I full admit that sometimes the problem is me.

Assuming that doesn't fix the problem, I'm going to shim it just to verify that THAT fixes the problem. I may buy new rings after that, but I want to make sure I'm actually fixing the problem, because it could always be something else.

So to shim it, what I'm hearing guys say is to shim under weaver base, right?

And if that's the case, given the fact that my POI is currently high and I cannot adjust the scope any lower, I should therefore shim under... [insert your answer here]?

Every time I think about this front or back question, I get a headache. Which is it? POI is too high. Shim under...

Thanks guys. Appreciate the advice.

Grouse
 
Quote:pOI is too high. Shim under...



Front.

Think of it this way, bullet hitting high, you want to raise the crosshairs, that forces you to point rifle lower to get CH on target.

Regards,
hm
 
I didn't see where you said what type of rifle it is, other than 22/250 but if the front and rear rings are interchangeable, you might try switching them. But I think the Burris ring suggestion is the best fix.
 


Write your reply...
Back
Top