shiming a scope?

I wouldn't call it a good practice, not really bad either though. The better option of course would be to buy some adjustable rings. With that being said, I have done it many times and so have lots of other people with no negative consequences. I've found a thin strip of aluminum from a soda can works very well! Good luck!

Stoti

I don't see the point of it. If you are using clicks for elevation adjustments, the vast majority are likely going to be up for shooting longer distances. Your scope likely won't focus below 10 yards and the adjustment for that will usually be less than one rotation down to compensate.

stoti has it right!

If you do dial for elevation as Hawkeye69 mentioned and you want the most available mil or moa for dialing elevation, you can do the following...

Before mounting your scope, make one full revolution clockwise(or more if you want) on your elevation turret. You then use the shims or adjustable rings that you asked about and finish mounting, centering and sighting in your scope. If you do this and use the shims to center your crosshairs and not the turrets, you'll have one full revolution of extra elevation for dialing on long range targets. In essence, you're just adjusting the crosshairs before sighting in the scope so that you can make more use of your scope's adjustment range. For the scope I use most often for long range shooting, this equates to 6 mil or 60 clicks of 1/10mil of added elevation adjustment. It can be very useful if you shoot long range and you find yourself running out of adjustment often. I didn't mention it because I don't know your intentions or if you even dial for elevation. Hope it helps! 

Stoti

If you do dial for elevation as Hawkeye69 mentioned and you want the most available mil or moa for dialing elevation, you can do the following...

Before mounting your scope, make one full revolution clockwise(or more if you want) on your elevation turret. You then use the shims or adjustable rings that you asked about and finish mounting, centering and sighting in your scope. If you do this and use the shims to center your crosshairs and not the turrets, you'll have one full revolution of extra elevation for dialing on long range targets. In essence, you're just adjusting the crosshairs before sighting in the scope so that you can make more use of your scope's adjustment range. For the scope I use most often for long range shooting, this equates to 6 mil or 60 clicks of 1/10mil of added elevation adjustment. It can be very useful if you shoot long range and you find yourself running out of adjustment often. I didn't mention it because I don't know your intentions or if you even dial for elevation. Hope it helps! 

Stoti

Click to expand...

That method will certainly work but some feel that a scope will function best with the adjustment mechanism near center. Personally, I use MOA bases for my "long range" shooting and keep the mechanism nearer center. Absolutely not certain that this helps scope stability/function but it works well for me.

I've heard that too but never had a problem. On my centerfire rifles I do use a 20moa base too, however, quality scopes should work fine throughout the adjustment range. If not, then the scope is worthless for dialing elevation.

Stoti

I've heard that too but never had a problem. On my centerfire rifles I do use a 20moa base too, however, quality scopes should work fine throughout the adjustment range. If not, then the scope is worthless for dialing elevation.

Stoti

Click to expand...

A scope could dial elevation perfectly well and still be most stable at/near the center of the mechanism. If your method works well for you by all means use it. Some others don't agree. I don't know which is correct and it may vary by scope maker but as noted I tend toward keeping my scopes near center of adjustment range.

I believe he is asking if a scope preforms best optically centered , and the real answer is , it depends on scope , alot of entry level and mid range scopes do preform better centered , however Higher end scopes , no they are designed for dialing turrets and it does not matter where the turret is dialed to , the image quality will be the same even outer edges . I spoken to hawke , Schmidt and bender and Niteforce and SWFA about this and They all got both answers , It depends on the quality of the turret linkages and lens and how things held together , like an entry scope may have a spring steel strip to hold elevation , where as a German Teir 1 scope the turret is held sold in 5 different points , so an entry level if cranked up all the way for a long time when u spin it can lose its tension and become erratic , but a 5 point system is designed for this and much more ,

Hope this helps LOU

With certain rifles that have No MOA built into the rail, 
certain scopes will run out of elevation 'clicks' at either short or long distances.. 

*Angling the scope can/will make up for that, and all for more adjustments..

Shimming is a practice, and it definitely works.. I won't get into the right/wrong though..
Too many people have too many opinions on that one..

Recently, I switched from using my Nikon scopes to Discovery scopes, 
and at the time up to current, also limited to shooting inside @ 10m 

I couldn't sight in any of the rifle/scope combos to save my life..
Multiple bullpups w/ 0 MOA rails, and two Disco VT-T 6-24x50 scopes..

Thanks to Hajimoto! - He suggested I grab a set of FX No Limit [Adjustable] rings, 
and give them a go, before I went the shimming route..
I got a set, and they worked Awesome! Now I have 2 sets, and they're my new go-go's.

I've been converted. Used to 'shim', now I just 'adjust'.
In MY case - This is much better because I swap scopes around on rifles so much.

If you're dedicating a scope to a rifle, and calling it good.. I suppose shimming is just fine, 
but, again in my case - I'll probably never go back..

 

Sam -

I always do it just to have a little more tension on the tube spring in the scope. The more tension on the spring the better it will hold zero.

I got in the practice of centering crosshairs using the mirror method of any scope before I mounted, then if I found the need to crank the turret more than I cared to during sight-in, I would shim. As mentioned, it clearly depends on the quality of the scope internals. But on recoiling spring guns I would likely shim higher end optics as well just out of habit and a bit more ease of knowing I've done what I can do relieving pressure on the internals.

Plastic from coffee can lids and other clear plastics of varying thickness' cut to ring size also work well.

I have one cheesy, beater BSA 6024 scope that ran out of elevation for 75 yard shooting. I paid $70 for the scope, and am not going to spend more than $10 for rings so adjustable rings are out of the question. I shimmed the scope and got pretty close to optical center at 75 yards. It doesn't take much, a bit of aluminum can is usually enough, and if that's not enough, a layer of electricians tape on top of the aluminum strip will usually be more than enough. 

While purists will point out that it's not good to angle a scope through the rings as it'll put pressure on the scope tube where the front ring contacts the tube, in my opinion (worth what you paid for it), the pressure is insignificant to add enough elevation to get my scope optically centered at 75 yards for an air rifle.

I have adjustable rings on my Impact, $70 for the rings and considering other options, that's darned expensive. eBay has NCSTAR adjustable rings for anywhere from $10 to $15 per ring (you need two). If you really wanted to cheap out, just buy one and see if you can mate it with your existing front ring.

As with a any solution, the cheapest (shimming) does work, but there are other relatively inexpensive options as well. The NCStar rings are adjusted by a screw, so easy to get it right.

Instead of shimming just purchase Burris Signature Zee Rings with posalign inserts.

i use them on every air rifle I own. Have replaceable inserts inside rings made to move POI without adjusting scope. Set of inserts come in +/- .005” increments up to .025”.

So many options to get the scope properly aligned. Shimming, the Burris Signature Zee Rings (that's a new one for me), and adjustable rings, and tapered bases are probably only a few of the many methods to elevate the rear of a scope.

That's why I like this sport, so many solutions to a single problem, the issue becomes making a decision on which works best for you.

By the way, the beater BSA scope I shimmed, little info. I used a strip of aluminum cut from a soda can, sandwiched between 2 layers of electricians tape. That was too much for my Marauder at 75 yards. Instead of being optically centered, I had to push the cross hairs the other direction past optically centered. It doesn't take much. I didn't believe how little it took until I tried it. Since that scope is my experimental platform, I may put it in the NCSTAR rings I just bought and see what happens. I should be able to optically center the scope, then sight at 75 yards (that's the yardage at Lee Kay in North Salt Lake), using the elevation screw on the rings. I'll figure that out once I get the Marauder up and shooting again. Down for maintenance at the moment.