Shimming a scope base

• Oct 16, 2017

• #1

Lilly001

Senior Member

I mounted a Leupold VXR on my new Henry 45-70.
Then came time to sight it in.
After bore sighting and zeroing at 50 yds went strait forward without any problems I moved out to 100 yds.
The first shot was low and left. I adjusted the settings and the next shot was dead on.
Now I intended to sight it 3" high at 100. So I tried to move the settings appropriately. To my surprise there was no movement available.
I am useing leupold mounts and rings and I checked all of the screws.
My question is can I shim the rear base with something like sheet brass or aluminum to give me more elevation? Or is there a better way to do it.

 

• Oct 16, 2017

• #2

wareagle700

Senior Member

Leupold sells scope base shims designed for just that. Not sure how it would work on a lever gun though. Another option is Burris Signature rings. You can use the +/- inserts to get a good bit of elevation.

 

• Oct 16, 2017

• #3

mattech

Deranged Throat-Puncher

Are you sure the front and rear rings and base aren't mixed up? I'm not sure if they are different or not, but may be worth measuring them.

 

• Oct 16, 2017

• #4

Lilly001

Senior Member

mattech said:

Are you sure the front and rear rings and base aren't mixed up? I'm not sure if they are different or not, but may be worth measuring them.

Click to expand...

It's the dovetail front, windage rear. So I got that correct.
I've looked at it and I can't see anything I did wrong.
The rifle is drilled and tapped, the base is secured with blue loctite and is seated flush. The rings (30mm) seem to be seated correctly.
I know some rifles are off a little, but this scope is supposed to have generous adjustment range.
I don't know what shim thickness it would take to give me 3" at 100 yds but I'll check on line to see if I can find some.
The rifle shoots sweet otherwise and it's dead on at 100 yds so it's not like I can't use it. I just need to be aware of my ranges and remember it's drop.

 

• Oct 16, 2017

• #5

kmckinnie

BOT KILLER MODERATOR

Staff member

Wouldn't shimming the rear up lower it more.
I don't know just asking.
Check what Matt said also.

 

• Oct 17, 2017

• #6

Lilly001

Senior Member

kmckinnie said:

Wouldn't shimming the rear up lower it more.
I don't know just asking.
Check what Matt said also.

Click to expand...

No. I am pretty sure rear sight up raises the point of impact.

 

• Oct 17, 2017

• #7

kmckinnie

BOT KILLER MODERATOR

Staff member

Lilly001 said:

No. I am pretty sure rear sight up raises the point of impact.

Click to expand...

The rear scope mount

It would point the scope down more. This is not open sights. Open sights raise the rear out further.
Maybe I still rong

 

• Oct 17, 2017

• #8

fishtail

Senior Member

I’m guessing you don’t want to shim the base.
Doing so will throw the square out of being able to tighten the rings to the tube of the scope evenly.
Burris and probably others have rings to do this job.

 

• Oct 17, 2017

• #9

fishtail

Senior Member

If you were to shim only one of the bases, wouldn’t you then need to lap the rings to straighten the offset out?

 

• Oct 18, 2017

• #10

Lilly001

Senior Member

fishtail said:

If you were to shim only one of the bases, wouldn’t you then need to lap the rings to straighten the offset out?

Click to expand...

I guess theoretically that would be true. But would .030 or so misalignment really put that much strain on the scope tube?
And would ,015-.030 shim be enough to get the 3" I am looking for?

 

• Oct 18, 2017

• #11

kmckinnie

BOT KILLER MODERATOR

Staff member

Can u post a pic of this rifle and scope on here.
A side view. Not real close shot and not one far away.

 

• Oct 18, 2017

• #12

S

spurrs and racks

Banned

Matthew Quigley

lives!

s&r

 

• Oct 18, 2017

• #13

wareagle700

Senior Member

Lilly001 said:

I guess theoretically that would be true. But would .030 or so misalignment really put that much strain on the scope tube?
And would ,015-.030 shim be enough to get the 3" I am looking for?

Click to expand...

Yes, that’s enough to misalignment to worry about. I’d lap or get some Burris rings.

A shim at the rear of .015-.020” will give you way more than 3” at 100 yards.

 

• Oct 18, 2017

• #14

Wooly Bugger

Member

Get DNZ or Talley mounts, always hear about shimming Leupold mounts, never an issue with the two mentioned. Stepped out of the box and tried the DNZ mounts to see how they are, well, took ALL my Leupold rings and mounts and replaced every one of them and chucked them in the trash where they belong and never looked back

 

• Oct 18, 2017

• #15

Lilly001

Senior Member

This is it.

 

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• Oct 18, 2017

• #16

Lilly001

Senior Member

If I shim the base, since it's a one piece, would that still miss align the rings?

 

• Oct 18, 2017

• #17

fishtail

Senior Member

No.
That information was useful.
Shim it.

 

• Oct 20, 2017

• #18

M

model88_308

Banned

Shimming a 1 piece base will not harm the scope whatsoever.

And, you're going to love that scope. I have 3 Leupold VX-Rs, two 2-7×33 and one 1.25-4×20

 

• Oct 20, 2017

• #19

Lukikus2

Senior Member

kmckinnie said:

Can u post a pic of this rifle and scope on here.
A side view. Not real close shot and not one far away.

Click to expand...

Peaked my interest to

A 45-70 hitting dead on at a 100 is pretty dad gum good to begin with.

Why a scope? Love the iron sights on those.

 

• Oct 21, 2017

• #20

J

james243

Member

You can calculate the amount of shim you need (roughly) by proportional right triangles. (1/3600)*inches between front and rear screw holes on the base = amount of shim to change impact 1 inch at 100 yards. Likely to be about 0.001 shim per inch poi shift.