Scope shims: A product for our future?

25 January 2005, 08:04

Cal Sibley

I have a Browning .308Win with a Bushnell Banner 6x18 on top. I'm at the top of my vertical adjustment and still hitting about 2" low with 168gr bullets. I like the scope model and just bought a new model Banner in 6x24. In the mounting instructions is a section on installing scope shims. I've never seen this before and am wondering if this is something new that we're apt to see more of in the future. Possibly the scope companies are cutting back on the amount of adjustment available to us. I don't really know for sure, but I am concerned. Anyone else experience this? Best wishes.

Cal - Montreal

26 January 2005, 02:06

Flippy

I usually cut them out of brass shimstock or thin aluminum (pop cans) depending on what thickness I need or the application.

Scope companies ARE getting cheaper for the most part, but this has been an ongoing problem as every scope/mount combination is somewhat unique.

JUST A TYPICAL WHITE GUY BITTERLY CLINGING TO GUNS AND RELIGION

Definition of HOPLOPHOBIA

"I'm the guy that originally wrote the 'assault weapons' ban." --- Former Vice President Joe Biden

09 April 2005, 23:50

sharpsman

Nearly every problem I have seen lately with gross scope misalignemt has been do to TWO factors NONE of which are the scope Manufacurers fault,really.

First, many factory rifles have misalligned barrels and or scope mount holes or dovetails.It is nearly impossible to get the scope's center in line with the bore under those conditions.

Second as scopes are offered in higher and higher power ranges(due to shooters "needing more power" ,the range of adjustment is LESS.That's why tactical scopes generally have 30mm tubes,to get more adjustment range.

In a 12x or higher 1" tubed scope it is darn tough to offer enough POI adjustment to compoenste for some of the poor machine work on many facorty rifles these days.

Most of the timne,it only takesd a few clicks of W&E to get a scope bore sighted, but when it takes more, it generally is NOT the scope makers fault.

15 July 2005, 21:29

Collins

I've got a one piece base on a Steyr BMG 50. Can I shim the rear of this? It's 3.125" between the clamp nuts. And it's got a SA 6-20-56 Mil-dot on it. Any idea how many thou' would be a MOA? I think I'm gonna need to break out the calculator for this!

20 July 2005, 07:20

CDH

Shims suck. Mine always liked to work loose, loctite and all, until I epoxy bedded them...just like a stock.

Try the burris signature rings if shims concern you.

Dunno if any of it would hold up to a BMG. I would think that a near perfect fit would be required on that, to distribute the forces better! Good luck!

21 July 2005, 20:01

sonofagun

quote:
Originally posted by Cal Sibley:
I have a Browning .308Win with a Bushnell Banner 6x18 on top. I'm at the top of my vertical adjustment and still hitting about 2" low with 168gr bullets. I like the scope model and just bought a new model Banner in 6x24. In the mounting instructions is a section on installing scope shims. I've never seen this before and am wondering if this is something new that we're apt to see more of in the future. Possibly the scope companies are cutting back on the amount of adjustment available to us. I don't really know for sure, but I am concerned. Anyone else experience this? Best wishes.

Cal - Montreal

Sounds like something any competent gunsmith could fix.

Can't resist:

Bring it to Dewey, he keeps a 5 lb hammer just for pounding the objective down until it's fixed!

Dewey, Cheetum, and Howe
Custom Gunsmiths

04 April 2006, 18:38

Don Slater

quote:
Originally posted by sharpsman:
Nearly every problem I have seen lately with gross scope misalignemt has been do to TWO factors NONE of which are the scope Manufacurers fault,really.

First, many factory rifles have misalligned barrels and or scope mount holes or dovetails.It is nearly impossible to get the scope's center in line with the bore under those conditions.

Second as scopes are offered in higher and higher power ranges(due to shooters "needing more power" ,the range of adjustment is LESS.That's why tactical scopes generally have 30mm tubes,to get more adjustment range.

In a 12x or higher 1" tubed scope it is darn tough to offer enough POI adjustment to compoenste for some of the poor machine work on many facorty rifles these days.

Most of the timne,it only takesd a few clicks of W&E to get a scope bore sighted, but when it takes more, it generally is NOT the scope makers fault.

Quit buying Winchesters!

09 April 2006, 03:04

HenryC470

quote:
Originally posted by Collins:
I've got a one piece base on a Steyr BMG 50. Can I shim the rear of this? It's 3.125" between the clamp nuts. And it's got a SA 6-20-56 Mil-dot on it. Any idea how many thou' would be a MOA? I think I'm gonna need to break out the calculator for this!

It's a similar triangles problem. Long, skinny similar triangles.

The ratio of a 1" displacement on your target to 100 yards is the same as the ratio of your shim height to your screw spacing.

100 yards is 3600"

1"/3600" = (shim height)/3.125"

or

(shim height) = (3.125/3600)" = 0.000868"

Just under a thousandth.

H. C.

26 April 2006, 02:33

srw

sounds to me like a new mount is needed. i have seen this happen , but usually from the wrong base or rings.

i will not mount any scope on shims ,when you use shims you change the diameter of your ring which may make your scope egg shaped when tightened. that scope then may be useless on any other setup.

16 June 2006, 09:43

Old Elk Hunter

I am so glad that shims are history. I use Burris Signature rings when an alignment problem occurs.

02 September 2006, 07:48

catboat

I have shimmed up bases (just did a JC Higgins FN mauser last week).

The problem with shimming one base of a two piece mounting system, is that the rings are not in line with each other, and will dent a scope when rings are tightened. The problem is eliminated if you use a one piece base, and shim UNDER the base. The rings stay in line.

12 September 2006, 01:46

CRUSHER

WHY not machine off the base to get things to fit
instead of raising the one end with shims lower the other by shortning the base

23 September 2006, 09:00

scr83jp

When my GS was alive he used business cards for shims that he'd cut strips off & shellac them letting them dry before inseting them,I watched him do it many times and it worked.

24 November 2006, 21:35

Juggernaut76

A buddy of mine had the same problem with a Howa Varminter. As it turns out, the receiver was machined wrong from the factory. You may have a similar problem. As per your question, shims may well be a "product for our future" as long as manufacturers are more concerned about a dollar than they are about making a quality product.