I have a Bushnell Banner 6x18 mounted on my .308Win. At the maximum elevation I'm still hitting about 2" low on my targets. I've ordered a set of scope shims from Sinclair which should correct the situation. I've never had this problem, rarely heard of anyone else having it until this year. I've read of it occurring 3 times this year alone and hope it's not something the manufacturers are doing that's reducing our adjustment abilities. Anyone here using the shims and have you been satisfied with it? Thanks and best wishes.

Cal - Montreal

Cal,
Yep.. i sure have.... in fact, it's sold commerically...

but, coke cans make great field implements...

iirc put a strip under the front and over the rear rings.

jeffe

Cal,

We use them all the time, both the commercial variety and some home - out of aluminum foil! - and never had any problems whatsoever.

When I mounted my 3-9x42 Kahles on my M700 CDL .280 I found that the rear ring had some gap between it and the base. I am using Leupold standaard dovetail rings and bases.

I used a feller guage and measured the gap to be .012". I got some .012" brass shim stock from work and made a shim.

Problem solved.

What type of mounts are you useing?

Would this method work for you?

Is this scope a "known" instrument?

If the mounts check out, I would suspect a problem with the glass.

Cal

Shims may not be the answer but it easy to check!!

You basic problem is that the centre line of the scope is point upwards from the barrel and that can be for of two reasons or a combination of both.

1)The dimensions on your action's receiver could be wrong and the rear could be too low or the front too high. This is easily tested by mount the scope and only tigtening the front ring down. If this is the problem then the scope will be just clear of the rear ring and you will be a able to push the scope up and down by a few thou. If this is the problems then the fix is shims under the base. If you place shims under the scope and you need 20 thou or so you might crush the scope tube and you will probaly be looking at 20 thou or more given you are still 2 inches low at 100 yards with full adjustment.

2) The receiver dimensions are OK but the barrel thread in the receiver is crooked and pointing down. Thus when the scopes adjustments are centred and the reticle put on the target at 100 yards the barrel my be pointing 20 or 30 inches low at 100 yards.

Attempting to fix this with shims is not good at all becasue you ending trying to bend the scope and/or bend the ring and base join.

The "home fix" for this is to bed the scope in the rings. You use some coke tin under the rear ring until the scope (with adjustments centred) roughly bore sights or points where the barrel is pointing at 100 yards. Don't clamp the rings down the scope just sits there so as to establish how much shim is needed to position the scope for bedding. When you bed the scope you do so with the shim left in the rear ring.

Thus the end result is the scope will mount at a slight downward angle and if all is perfect it will match the angle at which the barrel comes out of the receiver.

Devcon Titanium is the ideal and after it cured you take of the base and rings and throw them in boiling water for hour or so as it heat cures. However Devcon Titanium is very expensive for a one off job and ordinary Devcon (or similar epoxies) will work OK.

Mike

Ive used Blues method of removeing metal from the base bottom . I used a half round file , then some emery cloth on a piece of round bar stock .



I had a rear leupold 2 piece base that tilted up alittle on a mauser. I filed the base bottom till it mounted in plane with the the front . Set the scope in the ring bases and bore sighted it at 50 yds. and it was right on.

Burris Signature rings work very well. THey have inserts that go inside both the front ans rear rings. THey make offset inserts so you can adjust your rings for moth windage and elevation and keep your scope's internal adjustments pretty close to centered. THis is a very good thing for a couple of reasons. One, the scope ring inserts do a great job of holding the scope without making ring marks on the tube or denting and kinking it. Two, you are more likely to get less stress in the set up when using these rings. Three, the closer you can keep your scope's internal adjustments centered, the better things are.

This is nothing that the factories are intentionally doing. It comes from manufacturing tolerance stacking against you. It has always happened and always will. It comes from differeing heights in reciver bridges, concntrency of the barrel in the reciver, how bent the barrel is and if it is working for you or against you, how accurately the scope base holes are drilled and tapped.

Then there are the tolarances with the rings and bases, which are at least as loose as the tolerances on the actions. I have never measured it, but it seems to me that the most variability comes with Leupold "Redfield style" rings and bases. THis has absolutely no data to back it up. It probably comes from the fact that I have installed more of those than anything else. It seems that Gnetry and Talley's are the closest to center. But then I am usually putting them on rifles I have drilled and tapped and often barreled, so they are pretty straight to begin with. WHo knows.

Also, if you need to get more elevation, then it would be better if you could get some one to machine the front base down, giving you more elevation and elimninating the need for shims. But Burris Signatures are easier, cheaper, and more stress free way to go. Just food for thought

Folks been using shims for many years and its not something new..Factory guns are sometimes out of square with the world unfortunately....Be sure and set your scope in the center of its focal plane, before adding the shims...A scope that is not in or near its center focal plane tends to lose its zero from time to time and has caused many a hunter to have a nervous breakdown in his search for the reason his gun will not hold a zero! It will also effect the true accuracy of the rifle I have been told.

Most of my guns are mausers and they have been surface ground so that my scopes sight in with the scope at or near the center focal plane...

I've been using Reynolds wrap for years. I didn't even know commercial shims existed. Never had trouble with tim foil.

1) At the range I use layers of paper for shims.

2) In the shop I have used a perimeter fence of masking tape that shims and makes the mounts co- linear, and then glass bedded the mount to the receiver.

3) Lately I have been cutting a radius on the bottom of the mounts with a boring head, and the mounts held in modifed V blocks.

4) I want to do it next with a fly cutter.

When I look at Stratton's or Acker's books, it makes me think I should be doing more with the mill with the mounts.

This is a common problem. I have used many a shim over the years. I cut mine out of an aluminum beer can with a pair of scissors!