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Having trouble adjusting the scope to align with the bore sight.

AJA

Aluminum
Joined
Jan 11, 2007
Location
Illinois
I have mounted the scope to a new rifle and am trying to sight it in using a laser bore sighting tool. I am trying to vertically align the scope and the bore laser dot at a distance of about 25-30 yards. There is not enough vertical adjustment in the scope to achieve this. Is this because the scope is not parallel to the bore?
If I add about 0.030 to the rear of the scope mount(one piece mount), I can get the the scope and the laser dot aligned.
What am I doing wrong?
AJ
 
If you mention the gun type and make of the base it might help. It is very possible you are not doing anything wrong. The base or the rifle mounting surfaces could be irregular.
I would be careful with plain shims to correct the problem, seems like they would need to be tapered to prevent bending the scope, base, or receiver.
Possibly doing a taper cut on the bottom of the base would be a better idea.
Do you have a precision straight edge to identify which surface is discrepent?
 
Use plain flat shims between the receiver and the base. Search for instructions on how to center the cross hairs, do it, and then determine how much shim is needed.
 
I also have a rifle to adjust a scope to. The scope sits 3 1/2" above the bore, so I'd wonder at trying to adjust the cross hairs to line up with a laser bore light at 30 yards.
I'm wondering if it shouldn't be more like 100 yards, maybe in the evening so you can see the red dot. If the bullet met the cross hairs at 100 yards it would be high at 200, right?
So, if you got the dot and cross hairs to meet at 30 yards the bullet would be quite high at 100 yards. Is this not right?
 
There are laser boresighters and there are laser boresighters. The quality on some is so poor that the laser fails to align with the bore. Yours may be one that doesn't align. Can you rotate it to see if the dot moves?

PS: Boresighting only gets you close so shots should be on paper at shorter ranges. Best to shoot at 25 yds, adjust sights, then move to 50, 100, etc.

Boresighting = preliminary adjustment

Final adjustments must be done at the range.
 
First thing would be to view the target through the bore to make sure the laser is accurate.
On rifles where the scope mounts was added, as older military rifles or rifles that had originally only iron sights, the height of the front and back mount might not be in line. In one instance I had to mill the base of the front mount to correct this. Shimming under one of the mounts (if separate, like on those installed on Musers etc) will correct this, though not as elegant.
 
the type of rifle and mount are important info to have. That being said, I found some fellas at the range having trouble with their new AR/one piece mount, and the mount was a 20 moa mount which they had on backwards,...
 
AjA, Start by centering the crosshairs within the scope. Do this by placing scope body in v-blocks and pick a spot on a wall. While looking through the scope slowly rotate in v-blocks and adjust until crosshair intersection stays on your mark. Mechanical center is what you are looking for. You could do the same thing in the scope mounts with the tops of the rings removed as long as the turrets have clearance.
How high above the bore is the centerline of the scope? Do you have a bolt action? If yes remove bolt and sight through bore to a spot on a wall. Put ring caps on and look through scope. Are we close???

To answer your question, it sounds as if your scope mount or perhaps rings are not holding scope parallel to bore.
 
I would think that with the scope setting that high it would be hard to get both aligned at 30 yards. I would adjust the cross hairs to line up with the bore at 100 yards, although I would think that the lazer dot would be vary large at the 100 yard distance. At night I would place a small flashlight at 100 yards and look down the bore and align the sight that way.
If the scope is aligned at 100 yards, my guess is that it would be the same or lower at 200 yards (+/- 2 inches). Keep in mind I am a novice at siting in scopes.
 
I have made a scope alignment rod and bored it to accept a lazer bore site tool. With lazer site tools in both the rifle bore and the alignment rod, centered and zeroed, the dots diverge 1 inch at 10 yards and 7 inches at 40 yards. The lazer tools can be switched from bore to alignment tool with the same results. Does this tell me the barrel is bent?
 
Depending on the parallax of the scope and the height of the scope above the barrel I think it would be impossible to have enough adjustment if you are trying to center the cross hairs on the projected dot. Yes the bullet crosses the line of BORE twice but only intersects the sight path at point of aim say 150 yds. Because the line of sight at 30 yds. might still be 2" above that laser beam you need to creat a reference point to set your cross hairs to. You ar probably able toget your horizontal dialed in but are running out of vertical and if you did get your vertical your second crossing (point of aim) would be in timbuctoo yards.
 
I have mounted the scope to a new rifle and am trying to sight it in using a laser bore sighting tool. I am trying to vertically align the scope and the bore laser dot at a distance of about 25-30 yards. There is not enough vertical adjustment in the scope to achieve this. Is this because the scope is not parallel to the bore?
If I add about 0.030 to the rear of the scope mount(one piece mount), I can get the the scope and the laser dot aligned.
What am I doing wrong?
AJ

You've got a bunch of answers that should get you headed in the right direction.

The subject of where the the bullet goes after it leaves the barrel is called "exterior ballistics". So step one should be to use an exterior ballistics calculator and enter the information about your ammo's flight path, your scope height above bore, and your desired target distance to determine where the bullet is first going to cross the line of sight.

Federal Premium Ammunition -

From there you can see about adjusting the rear sight base height, if needed, to get the scope correctly aligned with respect to the bore. It may even be desireable to lap the scope rings as well.

Steve
 
AJA, if you can bore sight the scope at 100 yds without running out of scope adjustment, you might be OK. You don't need a laser. Just put the rifle in a solid rest and align the bore with a mark at 75 to 100 yds. A 2" square light colored sticker will do, or a contrasting color brick on your neighbor's house. It is easy to look down the bore and adjust the rifle's position to center the mark in the bore circle. Now look through the scope and try to adjust it to the mark. Don't let the rifle move. If you can get it set, your first shot should be on the paper at 100 yds. If the scope won't adjust far enough, I recommend Burris Signature rings with their eccentric inserts to get your scope better aligned. Ideally, the scope should be close to the bore sight mark with the adjustments centered, but it is not essential. What is essential is that your scope can be adjusted to zero your rifle at your desired range. You can do it if you approach the problem logically and think about the geometry.

RWO
 
............ It is easy to look down the bore ........

Not with a Garand or a Ruger 10/22 it's not! :D

This is the fun part of PM. When the OP makes a generic description of the problem without any of the important details and then we all get to make a bunch of guesses on how to fix the problem. :willy_nilly:

Steve
 
I would only trust a laser bore sighting tool to perhaps 2 to 5" close so would check with taking a shot. Very often one (laser) gets you on the paper. Then perhaps 5 shots to make dead on. ..for a 22cal 30 or 50 yards ok.. for a high power cal set at perhaps at 100 or 200yards best.

I like my barrel free floating so feel a .003/.004 shim under the barrel.. also never bench set the barrel on something as this can make it shoot way off. Give the scope a good knock with a hard plastic hammer or perhaps a hard wood knocker as this sets the cross hairs to rest and then they will not change as easy later down the road.
(put your oil rag on the caps and give a good knock then take another test shot.)Knock about like a hard knuckle knock on a door but yes with a hard knocker.

Guess I would find a plastic shim if a shim was needed.. .030 shim seems a lot .. you might put the action between centers and plate check the mount position to see that is in fact tapering the wrong way.. knowing the actual true error you might machine the mount bottom to make it right so no shim needed.

Do check for bugs and a screw bottoming out.

*Be dead sure before you modify..
 
I bought one of those laser bore sighter devices once. The kind that fits the chamber like a cartridge.

The gun was already sighted in. I though it might be a useful reference to have along on a hunt.

Mine was such a monumental POS, it wasn't good for anything except exercising cats and dogs.
 
A small mirror on a stick easily fits behind the barrel face.

RWO

Yeah, I've tried that. In theory it works fine, in practice getting the mirror tilted right is a pain in the ass. On my to do list is to make a small device that holds two mirrors that you drop onto the Garand's follower and keeps the mirrors lined up while giving a small space between to use the iron sights. At the rate I'm going I should have time to build it around 2042.

Steve
 
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Burris Signature rings with an offset insert kit should get your scope centered. As others said make sure your reticle is mechanically centered in the scope first.

The offset inserts can be used instead of base shims and also act as gimbals so that no bend is not placed on the scope.

Vlad
 
AjA, Start by centering the crosshairs within the scope. Do this by placing scope body in v-blocks and pick a spot on a wall. While looking through the scope slowly rotate in v-blocks and adjust until crosshair intersection stays on your mark. Mechanical center is what you are looking for. You could do the same thing in the scope mounts with the tops of the rings removed as long as the turrets have clearance.
How high above the bore is the centerline of the scope? Do you have a bolt action? If yes remove bolt and sight through bore to a spot on a wall. Put ring caps on and look through scope. Are we close???

To answer your question, it sounds as if your scope mount or perhaps rings are not holding scope parallel to bore.

Stand the scope on a mirror look down the scope and center the crosshairs .done


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