Airgun Academy Episode 42 - Shimming a Scope 

Enjoyed your articles for decades Tom, nice to finally see you in a video

Perfectly timed for me! I put new Barska scope on my RWS 36 break barrel and maxed out the elevation adjustment because it was shooting about 5" too low. So, I did two things, shimmed it up on the rear using an aluminum step flashing shim bent to a 1" radius and I reversed the scope mounts front to back. They were slightly different in height and the front had an adjustable set screw on it's underside. I adjusted it to a smidge up past the ring but not too much. Shot a bunch of pellets and zeroed it in at 20 yds which is my live target distance. Perfect, thanks!

Great illustration and explanation, Tom. Let me add a specific solution that eliminates the possibility of stressing the scope tube: Burris Signature Rings. Even if the scope needs no shimming or offsetting, regular rings can and commonly do stress scope tubes. The Signature Rings use plastic inserts that allow a gimbal effect between the rings and the scope via the spherical outward shape of the inserts. This makes the inserts conform beautifully to the scope tube while seating into the rings. Offset inserts can be bought to correct for up to 40 moa of correction, in any direction. This system helps keep the scope's adjustments at or near center, which gives the best optical performance. (No, I do not work for Burris or own stock in the company.)

If anyone is looking for shim stock ideas, I've used photographic film for shimming and it works really well

Thanks Tom you just sorted my problem. All the best from the UK

Great video! However, isn't that jig bending the barrel in the wrong direction?

Aluminum duct tape works the best, plus it has a sticky side. You can also shim under the mount. Works well with pica tinny rails.

Another option is to use Burris Signature scope rings with their offset inserts (sold separately). The inserts are free to pivot within the rings before you tighten the caps, so there is no issue with bending the scope itself. The offset inserts can be rotated to eliminate both vertical and horizontal scope/barrel misalignment. I've used them on two of my powder burners (M-14 and AR-15) and they hold the scopes more securely that any other rings I've tried.

I have a Gamo hornet maxim .22 and I am on my second UTG scope and still cant get the elevation high enough(shooting about an 1 1/2 low) when sighting it in at 25 yards, until I saw this video and I am dead on using Gorilla tape to shim it...thank you very much!!!!

Been fighting my Beeman R1 for years. can't crank the scope up enough. something changed

To avoid crushing the scope, you could also add equal shim washers where the screws tighten or buy a scope shim kit from brownells

Good info. Tom, thanks.

excellent video

you just saved me 70 bucks , thanks

Great video How about that rubbery electrical tape it's thick enough plus it doesn't scratch, and it has some gripping

I use Hawke 25moa shims on all my scopes. They are not very expensive but are properly angled so you don't crush the tube.

Easy to understand as always! Thanks

Do it the right way and get an adjustable mount to address elevation.

It's funny I watched your video and tried shimming my scope from the rear mount and was still way off wasn't hardly coming near the target so just for the hell I moved the ship to the front mount and had improvement right away before it was hitting way low and left and I had no room click wise now I'm getting close to center owe BTW I'm shooting a 22 Air venture Avenger bullpup and yes I got it at Pyramyd air awesome gun

A 20MOA rail is only a few thou difference front to back, so, it doesn't take much, if there is enough room between the ring base and rail or action, better off to put it there. Tape and such is OK to stop scope slippage inside the rings, but, keep it thin, real thin. And, Signature rings are the best solution overall, as you can transfer them and reset angles on the next gun or scope.

I love this channel!! was wandering... if you can't get a scope adjusted to were it still shoots low. can you shim the front tube?? Thanks much and blessings!!

Do I shim the front or the back if I'm 6 inches low at 30 yards?

i think that shimming is horrible for the scope. i recommend barrel droop mounts. nice video!

I have a TX200 which apparently has barrel bent up. I will shim the front ring..

I'm surprised my FX Wildcat MK3, which you can't even SEE the droopage or angle of the barrel all. An for being such an expensive airgun, I was surprised how bad it was off. Was shooting over a foot an half below the scopes cross hairs at like 50 yards. Man an if it's "worse" at closer range then far, that most mean it's WAY off.. idk feel like there may be some other issue, but we'll see how shimming and the adjustable mounts work when those come in.

Exactly what I needed to fix my air rifle scope.

Tried this on an Airsoft rifle and it solved the problem. Thanks!

Great video! thanks for the info

I cut out a piece from a soda can I folded it over then place electrical tape on it works great

Is barrel droop across the board on break barrel rifles or are some brands more prevalent? Good information.

I just used 3 pieces of electrical tape on my rear ring and it brought up my elevation nicely

Thanks great information

How do you shim for windage?

I haven't old Chinese air rifle that I've had for the last 27 years it's a underlever air rifle I want to put a scope on it but there's no way to attach it can you please let me know what is the best way

500ML curved plastic drink bottle worked for me as rifle was shooting 2" low on max elevation. 2 pieces needed. Now shooting spot on.

Pyramydair > Airgun Deopt

Finally a simple fix!

Is shiming to the right possible

That's y I always try mi guns without a scope first just to see if is shutting straight and then put a scope on

Tom Gaylord # 1 Airgun godfather

The term "barrel droop" is wrong. Why? If anything the correct term should be breech block droop. Its the breech block that is not aligned properly, and since the barrel is pressed into the breech, it follows the downward angle of the breech.

from som of the comnts i'm thnkng in trms of a breech blok shim . . .

Shimming scopes, bending barrels, can't the real problem be fixed somehow, by correcting the joining of the barrel to the spring cylinder? I mean, it appears that's the cause of the thing, why is everyone looking at work-a-rounds? Can't all the mechanisms be somehow adjusted so that the barrel and the cylinder meet at the same angle? -- And why is there a market for adjusting scope mounts, instead of a market for a kit to correct the problem? What an industry! Wouldn't it be nice if everyone's industry made accommodations for poor craftsmanship? "Oh, Mr. Accountant, don't worry about the mathematical errors, we expect your work to be off, so we wrote a compensating spreadsheet to put all your work through after you turn it in." "Oh, doctor, you sutured the wrong valve, but don't worry, we expect that from you so we've created a special compensating pacemaker to adjust for your shoddy surgery." Here's a post I've been leaving on other "compensation" videos which sums-up my thoughts on this 'compensation' thing nicely: You gotta be kiddin' me!! Instead of trying to correct the "barrel droop" - you compensate for it by shimming the scope!?!?? Well, then!!! > The next time my breaks are going on my car, I'll adjust my accelerator to not press so hard. > If the front end of my car goes out of alignment: No problem, I'll just adjust the rear axle to point sideways so I can drive straight. (No matter that the passengers-side of the car now travels down the highway in front.) > If I should get a tooth cavity, no problem, I'll just grind down all my teeth to match the depth of the cavity. > The next time my hard drive starts to click in my computer, no problem, I'll just mount sound dampeners around it. > I'd write more of these, but I have to go now because there is a very, very strong odor of gas in my house that's making me dizzy and I have to find the air-freshener spray. Cya!

I use electrical tape.

I used 5 shims on my air rifle 😂

If the gun is shutting to low take the barrel out put in a a clamp tight from the bridge block and grab the end of the barrel just pull in to u see the is straight

I like to use old 35mm film negatives or slides..

Hi love the videos' I haw a problem with my scope sliding in the rings its a hawk fast mount scope ,hawk rings on a Artimus sr1000s air rifle.What can I do to stop it .Pleas help