When to use shims?

[Longrifle2506]

I have an older Burris signature series 3-12x50 scope that I purchased in 1994. I just sighted it in and everything went well. But I had to take the elevation up about 20 inches. I looked at the erector tube from the objective end, and although it appears to be off center. It's not real far to any one side. It's not even close to touching an interior wall of the outer tube either. Doesn't look bad at all, and it Is very accurate. I had enough adjustment to zero it at least. And I shot 3/4 MOA after adjusting it.

My question is: is 20 inches too much? Should I adjust the erector tube back to center and shim the scope so I don't have to adjust near as much? Or: are Scopes made to adjust like this, and as long as you are within the Max adjustment range, it is fine to adjust the necessary clicks?

Thanks for your time

 

[LAGS]

I try to set up all my scopes with a laser bore sighter, or conventual Bore sighting, at 100 yards, With The Scope Set at ZERO/Zero adjustments.
And I am talking about Zeroing the scope on " V " blocks and not just counting the adjustment rotations.
With the scope at Zero, I bore sight it ,and see which way I have to shim the Base to be bore sighted at 100 yards with no scope adjustment.
On most mounts, that only holds true for the elevation , but some bases like the Leupold can be screw adjusted for windage.
By doing this, I can change to another scope set at Zero/ Zero adjustment, and it will reasonably be bore sighted same as the first scope using the Same set of rings, because the true Zero adjustment is setting the crosshairs to the outside diameter of the tube, which is not always the same as centered on your adjustment clicks or rotation.
Once I take the rifle to the range, I can see which way I need to adjust the scope adjustments, which is usually Minimal.
I will then have a scope that has almost all of the adjustment clicks in All Directions.
Most " NEW " rifle scopes are set at the factory with a Zero/ Zero setting to the scope tube.
It is a lot of work, and most gun owners or even gunshops will not go thru all these steps.
But if you want it done right, then just make that little bit of effort to make it better.

 

[Longrifle2506]

Yeah I hate to go through the effort and have to shoot more $2 per round Barnes vortex ammo but It would be done The right way. I know there are tons of people who click away on the adjustments, but I would feel much better if it was zero/zero.

 

[rcmodel]

but I would feel much better if it was zero/zero.

Good luck with that with a 3-12x variable scope!!

rc

 

[Longrifle2506]

I doubt I will achieve zero/zero but I can minimize the adjustment greatly. I guess I will note the location on my boresighters grid pattern that the reticle is now; then take the elevation back to center; then try to get as close as I can to the noted location on the grid pattern by shimming under the tube of the front ring.

 

[sappyg]

I'm kinda in the same boat here. After many years I retired the Redfield 2x7 from a fwt. .243 and installed a VX-1 2x7. Nice scope but I bottomed out at 100 yards at dead on zero. Not sure if I'm gonna shim the scope because I'm at zero on the target. I can go up but not down.

 

[LAGS]

A Longrifle25-06
I think your first mistake is trying to use a Grid Pattern to Bore sight your rifle.
You need actual distance to set things right
I sight mine in at the power pole that is over 100 yards away in the early evening when I can see the laser dot on the pole.
The least distance I set a scope is looking thru the bore at the Garage door handle on the house across the street which is like 50 yards.
But After I sight in my rifles, I recheck with the Bore sighter and record where the Set adjustment for that rifle is.
Laser Bore Sighters are only Close , to get you on paper at 100 yards.
The more you use your laser bore sighter and recheck after sighting it in, then you will know how true your bore sighter really is.
then you can compinsate and get closer bore sighting adjustments the first time.

@ rcmodel
Why is your scope changing Zero when you change Power settings on bore sighting ?
It shouldnt change your adjustment when you change your power in the field.
With the crosshairs set to center of your scope tube, it stays the same as your scope rotates in the axis of the rings.
The power should not effect it.

 

[LAGS]

@ Sappyg
Many of my friends who are long range shooters, ask me to set their scopes to be sighted in at 100 yards with the scope set to almost the Lowest or Down setting like yours is.
That way they have all the UP adjustment they need to go out to greater distances past 500 yards.
As long as you will never shoot at less than 100 yards, and have to adjust your scope for that, then I would just leave it alone.
But for the average shooter, it is better to set it for a Zero scope at 100 yards.

 

[Longrifle2506]

I agree that the grid pattern is not a very good boresighter, doesn't get you on the paper necessarily, but it's great when switching to a new scope. Or if I take this scope off and put back on. Several times, the grid pattern has allowed me to note where my reticle is on the existing scope, then mount the new scope, move the reticle to the exact same grid location as the previous scope. Then I am dead on with the new scope. It is flawless when I use the same mounts but it can be a little off when using different mounts. That's all I want use the grid pattern for. If I shim the scope, then this technique will get me very close to the zero I have before shimming. It may take some convincing for some of you guys. But I have used this technique and it's Saved me lots of expensive ammo. I have switched scopes and upgraded scopes a lot.

 

[Longrifle2506]

I have to shim the ring; rear ring; no bases on my rig. Ringmounts

Ok well I shimmed it with 5 pieces of pop can material. Now I am only 5 inches from center elevation instead of 20 inches like before. I feel much better about that. Just gotta shoot a couple more rounds. Using the grid pattern technique, I may be dead on or I may have to adjust one to two clicks worst case. Thanks for the replies guys. Many people would have left it alone but I am a worrier when it comes to stuff like this so I did it to ease my mind.

 

[LAGS]

@ Longrifle2506
What rifle do you have with only Ring Mounts ?
Scope rings can also be Lapped to correct some deficiencies.

 

[Longrifle2506]

Sako 75 finnlight; actually the old OPTilock mount's consisted of bases and rings but I dislike them. I like the ring mounts that just have a large keeper screw that holds them to the taper dovetail receiver. OPTilock is making new ringmounts and they've only been out for a couple years. I have a pair of lynx ringmounts on the rifle. They are very good as they have a recoil pin just like the OPTi locks.

 

[xfyrfiter]

I guess I have been lucky! The last three scopes I have mounted only needed 2 or 3 clicks to boresight and 2 or 3 more or less at the range.

 

[Longrifle2506]

It's nice when it goes that well. I've had many sight-in sessions go like that also; this is only the second scope I have ever shimmed.

 

[LAGS]

@ longrifle 2506
I am not in favor of shimming the scope by putting shims under the scope tube on top of the rings.
But it can be done.
The shims can not be the full width of the ring bearing surface, or they are shrinking the width of the ring as well as the bottom dimention.
And if you only shim the very center of the bottom radius of your scope ring, then when the top ring is tightened, it is putting unequal pressure on the center of the bottom of your scope tube.
That can make the scope tube go out of round and effect your accuracy, as well as the ring not being able to be fully tightened.
But I have used Epoxy to Bed the rings to add height to one ring where I had ring mount guns.
You put a shim in the very center of the bottom of the ring like maybe 1/4" wide, and then bed the scope in only snug with the epoxy in the ring, and release agent on the scope tube or mandral you choose to use.
Then when dried, the bottom half of the ring is raised inside, and will have full bearing contact on the bottom of the scope tube.
But if there is not too much height adjustment needed, then I opt to Lower the other ring seat by Lapping it in with a scope lapping Bar set up.

 

[Longrifle2506]

I actually have a lapping bar kit. I have never lapped rings yet; nor have I done any type of bedding. I wish i did. This was only the second time I have ever used shims. I only had to fire one shot today and thanks to noting my reticle location on the grid pattern before shimming the scope, It was dead on. I will include a couple pics.
URL=http://s258.photobucket.com/user/wileykia2506/media/Mobile%20Uploads/image-1.jpg.html] [/URL]
http://s258.photobucket.com/user/wileykia2506/media/Mobile Uploads/image.jpg.html] [/URL]
To better explain things, I just drew myself a grid pattern and marked a little crosshair where my reticle was located on the boresighter grid; I took the scope out of the rings and shimmed the rear ring and then I put the scope back in the rings and torqued the screws Down(17-18 inch pounds). I used click adjustments to get my reticle to that exact same spot it was before on the boresighter grid. Thanks to the shims, i only needed 20 clicks to get my zero; where without the shims i needed 80 clicks. Then today I fired one shot and the target is pictured above. That is 135 yards and it is 1 inch high. It is pretty much a 200 yard zero and I am comfortable with it and I don't see any need to crank the adjustments at all with an impact that perfect. If I would have just put the scope back in and went back to shooting without using the grid to get me back to zero, it would have required several more rounds of ammo to get it to a satisfactory zero. Barnes vor-tx 25-06 ammo is over $2 per cartridge. I am very happy with the rifle now. the Barnes 100 grain TTSX is more accurate than 85 grain ballistic silvertips; at least out of my rifle.

 

[greyling22]

It's not just you.

For whatever it's worth, I had a rifle that I guess the receiver is off or something, because I wound up about 40" low at 100 yds. I stared with weaver bases and rings, then went to warne bases and rings, and tried 3 different scopes. 40" low ever time. I would up using the burris posalign rings to shift the scope 30moa, which allowed me to get on target using fairly minimal scope adjustment. What a mess. (project rifle was something of a mess from day one though. Cheap barreled action was a zastava mini mauser in left hand, bought from charles daley when they went under. limited aftermarket parts, no customer support, etc. It wound up shooting quite well, but oh my goodness and I ever upside down on this rifle. If I paid myself $10/hr in labor, plus parts @ cost I probably have $3K in a rifle I couldn't sell for $500. I keep it as a reminder lesson every time my wife says "lets fix up a house" )

 

[LAGS]

@ Greyling22
But look at all the experience and Knowledge you have aquired.
If you put that in the bank for your next rifle, you will be a Millionaire.
It is not about the cost of our time.
It is about beating a bad rifle into submission.
You did that, so you won the game.