What to do when scope won't adjust far enough

[Jack Straw]

I guess you can see that I have a number of gun issues that I need to take care of...

I just put a scope on my old Remington .22 and took it out today to sight it in. I adjusted the thing up as far as possible but at 25 yards it still shot about 4 inches low. Now what? The scope worked perfectly fine on a .308 so I don' think that is the problem.

Thanks,
Jack

[Kernel]

Jack,

There are a lot of different ways to correct this problem. The easiest is to make some shims out of an old beer can. First take the scope off and mechanically re-zero it, i.e., dial it back to the center of it's range. Place the shims on the bottom of the front ring. Start with three shims, put the scope back on and shoot. Add or subtract shims until the scope is roughly zeroed. Once your within 2 - 3" of the aiming point then you can use the clicks on the scope to fine-tune.

Other fixes include lapping the rear ring, shimming or lapping the base, or buying Burris POS-ALIGN rings. All valid fixes, first I'd try the old tried and true "beer can shim." -- Kernel

[C.R.Sam]

Kernel nailed it.

sam

[Jack Straw]

Thanks for the replies. Dad and I discussed it on the way home and the idea of a shim came up, we just weren't sure that it would actually work or how much to use.

One thing I'm confused about is which end of the scope to shim since the gun is shooting low. Can someone explain why the front of the scope should be shimmed? My brain isn't working to well with the concept of sights today. Dad's Christmas present was a Ruger 10/22 that was hitting high and to the right today and for some reason I kept wanting to move the rear sight in the wrong direction. Some days it just doesn't pay to skip that second cup of coffee.

Jack

[C.R.Sam]

Oooops......you want to shim the rear to bring point of impact up toward the crosshairs.

Reread your first post......might want to shoot it again and adjust scope the other way just to make sure it really neads shimmin.

Sam

[Kernel]

Ooops. My bad. Putting the shims under the rear ring will bring the point of impact up. For can-stock I recommend Miller High Life Light. (which is what I was drinking when I gave the wrong advice earlier). -- Kernel

[Freedom in theSkies]

I had to do some shimming on a Mini-14 a while back. I used the same sort of technique, with the exception of using aircraft type shim stock. -It comes in large sheets and is about 1/4 inch thick. (250 layers of aluminum) Same basic idea, but you just peel off a piecethat is the right thickness and trim it to size. The main thing is, it worked.

[zot]

I like Milwaukees Best Ice for shims the best.

[dZ]

i prefer German beer cans
the tolerences are tighter

[HunterChick]

Well, what should I use? I drink Whisky!

[ZeSpectre]

well, drink more, it won't improve your aim but you won't care either I suppose

[croc4]

you might want to look at burris signature rings, they come with adjustable inserts that allow you to do major scope adjustments, then you can use the scope adj to fine tune. Plus the nylon inserts don't mar the scope finish.

my 2c,

Croc4

[mega twin]

Might try just swapping your rings from front to back first.

[CowTowner]

Might try just swapping your rings from front to back first.

I think mega twin is going in the right direction with that piece of advice. +1

[sikashooter21]

I was stuck bad when for some reason both my shotgun and muzzleloader had this same issue with being out of the scopes adjustment. It took a year to find the suggestions I found in this thread. The shooting range opened back up after they took advantage of a closing for COVID19 to update the range.

I was about to use the muzzleloader hunting so I used the shim technique described above. Three aluminum can strip shims, and my muzzleloader was back in business. I have a couple weeks before my shotgun goes deer hunting so I tried switching the front and rear scope mounts. That was easier and also solved the problem. I am happy to have found this site because nobody I talked to had a suggestion that worked other than replacing both scopes. But I viewed that as a last resort. If anyone has this issue both methods work great but I would swap the front and rear scope mounts first.

Thanks you Mega Twin, and Kernel. You saved the day.

[Scorch]

There are a lot of different ways to correct this problem. The easiest is to make some shims out of an old beer can

If you do the math, you will find that 4" at 25 yds translates to .017" higher at the rear ring. Since your scope is maxed out, I would suggest .030" shim under the rear ring.

[Mal H]

Administrator Note

Please note that this thread is over a decade old, so replies to posts other than post #15 probably aren't necessary.

[Bart B.]

Originally Posted by Kernel

First take the scope off and mechanically re-zero it, i.e., dial it back to the center of it's range.

I've never seen a scope whose adjustments are at zero (inside erector tube and its lenses on the optical axis that's centered in the main outer tube) when adjustment knobs are centered mechanically. There's typically more clicks up and right from zero to the physical limits. Many scopes inner tubes reach the limits before clicking stops.

Best way is to put the scope in two V blocks then look through and twist it adjusting until the line of sight stays at one place downrange.

Most scopes are zeroed when new. Adjust the new scope elevation knob up (or down) counting clicks to its stop, record the count, then adjust back the same number.

Repeat this with windage.

Verifying can be made using 2 V blocks

[Unclenick]

If you need to zero a scope, build yourself one of these:



Tall Nylon screws on a flat board also work, but are more prone to flex if they are long enough to allow some scope's adjustment knobs to go around without touching the board.



All the old suggestions in this thread to shim rings (except when lapping) have the potential to ring the scope tube by squeezing it against the edges of the rings at a slight angle, which can indent it. The Burris Signature rings with the ball-and-socket principle liners that adjust to the right angle without favoring one edge of the ring or another will solve that, but that ads more expense, of course, unless you have them already.

I think if we assume a scope with at least 30 moa of elevation adjustment from center, the gun in the old original post that was still 4" low with the scope adjusted all the way up was looking about 45 moa low. If it were 1.5" above and truly parallel to the bore line, the needed adjustment for a .22 RF at 25 and 50 yards (where the zeroes cross over) would be 8.4 moa above the scope zero, as found above. The large error reported indicated a more severe problem than is normally encountered; either a bent barrel or, as suggested, reversed rings for a receiver that has about 0.040" different mount point heights for the scope rings and requires a ring set especially for that gun.

[Bart B.]

Spinning a scope in V blocks to verify the line of sight goes straight out of its objective lens (on the scope's optical axis from the center of the rear eyepiece lens to the center of the front objective lens) is exactly like spinning a cartridge in V blocks to verify the bullet axis is aligned with the case axis.

[Unclenick]

Yep. And, in fact, the first time I saw the idea was when Stoney Point was marketing a little pair of plastic V-blocks for the purpose. They discontinued that product, which is why I came up with the home-made version.

[Drm50]

#1 run scope to end of adjustments. Then click all the way up through counting clicks. Do this on vertical and horizontal. Run clicks back to 1/2 way on both, then attempt to sight in.
On some scopes that be on a rifle a long time I use a piece of 1/2” wood dowel to lightly tap tube.

[Bart B.]

It's fascinating to me that some places say both methods work very well.

In spite of the fact that their results are not the same. Only one is correct.

The mirror method is darn near as good as the V blocks one.

If you've ever looked at the design blueprints of scopes, you'll see all the lenses are centered on the line of sight axis from the two end lens centers that's centered in the main outer tube.

https://patents.google.com/patent/US4643542A/en

[Unclenick]

On some 'scopes, I can feel the adjustment range squeezing a bit tight at the end of its travel and with no exact hard stop to count from, so I don't trust half the total number of clicks to be exactly symmetrical on either side of optical neutral (on-axis), and on a few scopes the difference is substantial. I also have one old scope that doesn't have clicks; just continuous adjustment. The spinning method is accurate for both situations, but I've never actually used the mirror method—only read about it—so I don't know how it compares to spinning for resolution.

[Bart B.]

The first time I twisted a knob counter clockwise away from the scope watching the reticle move away from optical center, it stopped moving but the knob went many more clicks to its limit. Different amounts for each.

Twisting them clockwise toward the scope, no more clicks after the reticle stopped moving.

Several scopes behaved the same.