Question about shimming scope rings

T

tpcollins

New member
I have a crossbow scope with 92 MOA travel - 46 MOA each way from the center. But it is lined up right now with only 36 clicks available to the left and 55 clicks to the right, which messes up the farthest yardage using the elevation turret as the erector tube may be bumping the inside of the scope tube (that's what Vortex said).

I want to get it closer to the center position by laterally shimming the rear ring. But doing that could put stress on the tube sides since they're not concentric (probably aren't now as it is).

Is this ok to do on 30mm tube or must they be lapped now because of the minor misalignment? Thanks.
 
Cut 2 shims from a soda can and stick them in there. Each shim is about .004" thick.

Keep shims on one side of the ring split. If split horizontal, top or bottom of the ring.
 
Makes no sense. If you have adjustment left, you have no need to shim. Also, left and right have no bearing on how far you can shoot, up and down does that. Suggestion: get a xbow scope with mil dots or stadia lines in it. Most xbow scopes are that way to begin with.
 
10 clicks isn't anything to care about. Set it and forget it.
4 clicks equals an inch at 100 yards. 16 clicks equals an inch at 25 yards.
 
Evidently I deleted the first part when I edited it but the crossbow scope is 1 MOA per click. So with 46 clicks from the center position, the 9 clicks from it is about 20% of the travel - not sure if it's relevant or not but when I use the elevation turret for yardages compared to the reticle, the poi moves to the right as I indicated.

Where others are saying to put the shims is confusing. Are you suggesting to put it inside the scope ring next to the scope tube? I was thinking of bending some thin brass stock at right angles and put it between the outside edge of picatinny rail and the inside of the fixed section of the mount that clamps against the picatinny.

My concern is how much shimming can I do before the shimmed and unshimmed rings compromise the scope's tube?
 
Evidently I deleted the first part when I edited it but the crossbow scope is 1 MOA per click. So with 46 clicks from the center position, the 9 clicks from it is about 20% of the travel - not sure if it's relevant or not but when I use the elevation turret for yardages compared to the reticle, the poi moves to the right as I indicated.
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If you're moving the "elevation" turret and the scope's moving to the right, you have the scope mounted 90 degrees off. You've put the elevation turret on the side and the R-L turret on top.
 
I think you need to post up a picture of your rig. What is it exactly. I shoot a Barnett Veloci-Raptor and don't trust any store with setting things up for me.

I've seen to many cockeyed adjustments. Remove the scope, remove the rings, remove the base if it comes off. Then place the crossbow in a gunvise, arrangement of pillows or something to keep it steady and reassemble keeping things level and retest.

Your POI can also move if you're holding the crossbow wrong. Cocked a bit to one side or the other will throw you off as you move farther away from the target.
 
Here's my Scorpyd Ventilator with the Vortex XBR scope. It has a scope level as well to keep it horizontal when shooting. The one problem with Scorpyd is their short crappy scope rails so I'm hostage to extended ring mounts. I tried several brands but the crappy Hawke mounts were what I liked as far as height.

The XBR scope is basically the Vortex Viper Series with a different recticle in MOA and 1 MOA per click. With the article in equidistant MOA, it doesn't align with crossbow trajectories very well. But with it on 4x, and keeping the trajectory apex between the 50 & 60 yard chevrons, I can use it to shoot 31-41-50-59-68 yards very well.

But I can also turn up the magnification and use the turret for the yardages as well. The end of the turret up is 70 yards, but because the windage is 20% off center, the erector tube is hitting the side of the scope tube when the elevation maxes out and it skews the poi to the right.

I think it's the cheapass Hawke rings. I may try to take the rear ring and turn it around 180 degrees to see it it gets closer to the scope's center position. Otherwise I'll spend some money for a better mounting system.



 
You do seem to have a lot going on there. Have you tried asking people over on the Crossbow Nation forum. They have a lot of knowledgeable guys there and some are prostaff to certain crossbow brands.

Seems like there has to be an easy way to solve your problem and have the level, top rail and whatever is under your zoom ring on the scope. That has to be the longest crossbow scope i've seen.
 
You do seem to have a lot going on there. Have you tried asking people over on the Crossbow Nation forum. They have a lot of knowledgeable guys there and some are prostaff to certain crossbow brands.

Seems like there has to be an easy way to solve your problem and have the level, top rail and whatever is under your zoom ring on the scope. That has to be the longest crossbow scope i've seen.
Click to expand...

My original question was:

I want to get it closer to the center position by laterally shimming the rear ring. But doing that could put stress on the tube sides since they're not concentric (probably aren't now as it is).

Is this ok to do on 30mm tube or must they be lapped now because of the minor misalignment? Thanks.
Click to expand...




I would have thought guys from the Smithy forum of the Firing Line would have more expertise in answering my question on the subject but maybe I was wrong - my bad.
 
When you say

Quote:
31-41-50-59-68 yards very well.

Are you saying that the cross-airs line up perfectly to shoot those yardages and then when you hit 70 yards the scope jumps off for POI?
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The XBR scope is basically the Vortex Viper Series with a different recticle in MOA and 1 MOA per click. With the reticle in equidistant MOA, it doesn't align with crossbow trajectories very well. But with it on 4x, and keeping the trajectory apex between the 50 & 60 yard chevrons, I can use it to shoot 31-41-50-59-68 yards very well.

But I can also turn up the magnification and use the turret for the yardages as well. The end of the turret up is 70 yards, but because the windage is 20% off center, the erector tube is hitting the side of the scope tube when the elevation maxes out and it skews the poi to the right.
Click to expand...


I'm pretty sure I referenced using the scope's reticle to shoot 31-68 yards very well, and I'm pretty sure I referenced using the turret to dial up the various yardages with the issue being at the end of the travel which is 70 yards.

But all of these questions are irrelevant because nobody addressed my original concern. Thanks for the help, I'll figure it out.
 
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I suggest you visit archerytalk.com and go to the crossbow sub-forum. You'll learn a bit about scopes and how they're used on crossbows. From reading your OP and following the responses it sounds to me like you don't understand how to properly use/mount/adjust a scope and you don't understand how they're used on crossbows. No offense intended, but you won't get a good answer here until you yourself have a better understanding. If's difficult for other people to answer your questions if you don't understand their answers. Good luck with this.
 
Shim the scope inside the rings with thin metal. No need to lap.
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In lieu of shimming between the ring base and the scope rail? I'm not sure how much room - if any - there is between the inside of the 30mm rings and the scope's tube?



NoSecondBest - I am a member of ArcheryTalk/CrossbowTalk and Crossbow Nation already. It is not a crossbow question - it's a shimming a scope question whether it's on a crossbow, rifle, BB gun or a pea shooter. Thanks for all the help.

If there's a way to delete this post then I'm good.
 
There should be enough room to shim what you need. Pieces of pop cans make great shims. Shouldn't take much.

Were the Crossbow Nation people not willing to help? Someone has to have your same setup there.
 
There should be enough room to shim what you need. Pieces of pop cans make great shims. Shouldn't take much.

Were the Crossbow Nation people not willing to help? Someone has to have your same setup there.
Click to expand...

I didn't even ask - since it was a scope shimming question, I just made the assumption that the guys here on the gunsmith sub-forum of The Firing Line were a helluva lot more competent on scopes and mounts than some bowhunters, irregardless what it is mounted on.

If rotating the rear scope ring doesn't get the scope back to the center position for horizontal, I'm going to get the Nikon M-Series XR mount with the 20 MOA slope, as it appears to have "windage adjustable" mounting plates on each side.

With that mount I can just center the scope and use the side mounts to adjust the horizontal until the POI is dead nuts. :)
 
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