Shimming

lefthooker

Hiya lads, went to set up my new scope today & after a bit of tweaking got zero with literally the last few clicks of elevation.

So what I'm wondering is should I get my base shimmed r stick with things as they are? Have many had this job done, what's involved & how much cud I expect to gain? & can it be done with weaver bases?

Deise Musashi

I've shimmed my own scopes before using a set of feeler gauges.

Slip them under whichever scope ring needs to be raised and try the various thicknesses to get on or very near target without adjusting the turrets. Tighten everything down and final zero using turret adjustments.

I'm not sure it's as necessary anymore with the better glassware available now. If your on the outer limits of your adjustment then there may be funny things happening with the lenses, bending light on the outer rims of the glass?

Feeler gauges are very cheap and you can mix and match to get best fit under the blocks, give it a go.

Cass

A few things.

What rail have you? what size are the rings/bases? What are the dimensions of your scope? (Objective lens/ocular lens/tube) What is the clearence between your objective lens and the rifle barrel?

lefthooker

ezridax wrote: »

A few things.

What rail have you? what size are the rings/bases? What are the dimensions of your scope? (Objective lens/ocular lens/tube) What is the clearence between your objective lens and the rifle barrel?

I have the weaver bases that come with the savage mkII , the rings are nikko stirling platinum medium & the scope is bushnell legend 5-15x40 AO - 52ml obj 44ml eye 1" tube. Clearance is 2/3ml.

Lads what are feeler gauges & where do I get them? Is shimming something I should leave to a gun dealer?

Deise Musashi

Feeler gauges are used by fitters/ mechanics etc. to precisely measure gaps.

They usually fold out and are like steel leaves in various thicknesses. Lads at works have some really long ones but you need the bog standard ones, you'll be cutting them anyway!



This is a job you can do for yourself, if your at the top of adjustment on the scope, raise the front block up. Bottomed out? Raise the rear block up to suit. Try to use only one shim of the right thickness to get the movement you need, you don't need anything moving under there!

It's like putting a bit of wood under something to level it up, the pressure of tightening the mounts holds it all in place.

clivej

Here is a guide for using a shim under the mounts to give you extra elevation on your scopes.
Use a cut up feeler gauge for the shim and you will have the correct thickness shim.

Bushnell Scopes made the data.

lefthooker

Looks awfully like the booklet that comes with the scope, me thinks clive.
Its the back base that needs shimming. Will I have to remove the recoil lug to do the job properly.
Strange thing is this happened before, was with a busnell too.

Dvs

lefthooker wrote: »

Looks awfully like the booklet that comes with the scope, me thinks clive.

Tackleberrywho

Deise Musashi wrote: »

I've shimmed my own scopes before using a set of feeler gauges.

Slip them under whichever scope ring needs to be raised and try the various thicknesses to get on or very near target without adjusting the turrets. Tighten everything down and final zero using turret adjustments.

I'm not sure it's as necessary anymore with the better glassware available now. If your on the outer limits of your adjustment then there may be funny things happening with the lenses, bending light on the outer rims of the glass?

Feeler gauges are very cheap and you can mix and match to get best fit under the blocks, give it a go.

A great idea as the gauge is a precise size and cheap to buy
I saw a lad using bricket rappers years ago on a Swedish mauser, and he had the bolt hacked with a round file(Long story, Mauser bolt is different)
Cut shim length of base, dripp holes to math base holes. then attach, try your local Nuts and bolts/Engineering shop for longer screws same pitch thread if necessary to get height.
Failing that buy higher mounts;)

lefthooker

Dvs wrote: »

I just meant the shim guide came in the box with the scope. Hope that clears things up.

clivej

lefthooker wrote: »

Looks awfully like the booklet that comes with the scope, me thinks clive.
Its the back base that needs shimming. Will I have to remove the recoil lug to do the job properly.
Strange thing is this happened before, was with a busnell too.

lefthooker wrote: »

I just meant the shim guide came in the box with the scope. Hope that clears things up.

As I said it's from Bushnell but the info does not come with the scopes now, well not with the 4 I have.
I'm not sure if you will need to lap the rings out as well.

lefthooker

clivej wrote: »

As I said it's from Bushnell but the info does not come with the scopes now, well not with the 4 I have.
I'm not sure if you will need to lap the rings out as well.

TBH there was so much literature in the box I was surprised they got the scope in; instructions, shim guide, warranty & reg card.

What exactly is lapping?

Deise Musashi

Lapping is polishing out with very fine abrasives, shouldn't be necessary lad.

If it were I'd be inclined to get different mounts!

clivej

lefthooker wrote: »

TBH there was so much literature in the box I was surprised they got the scope in; instructions, shim guide, warranty & reg card.

What exactly is lapping?

Because the scope in the mounts are NOT now square, because a shim will lift one end up, the mounts could squeeze the scope tube.
Lapping is done wth a round bar with lapping paste on, the same size as the scope tube, to grind a little off the mounts and let the scope fit perfect in the mounts.

Jonty

lefthooker wrote: »

Hiya lads, went to set up my new scope today & after a bit of tweaking got zero with literally the last few clicks of elevation.

So what I'm wondering is should I get my base shimmed r stick with things as they are? Have many had this job done, what's involved & how much cud I expect to gain? & can it be done with weaver bases?

OP if you are running out of adjustment, before you shim, remove scope and swap the mounts around, remount and zero and see if there's any difference

Cass

A friend had the same problem only in reverse. Could not come down enough to get a 100 yds zero. After going over his rifle i noticed his scope was very high up. Turns out he had high rings on when medium rings were the right choice. He changed rings and a week later was back on the range. Was able to get a zero at 50yds and all the way out to 600yds.

You're situation seems the same. I would check the rings. Try another set of higher rings and see if you can get a zero. The scope you have has 50" of adjustment at 100yds. Assuming its a .25" click value @100yds then then there is 200 clicks or 50moa total elevation adjustment. If you have expended all clicks/moa to get a 100yd zero then a shim may not solve your problem. Multiple shims will but if you need 3/6/10 shims i would look at changing the ring(s) first. Maybe a 20 moa base. They are usually 7/11mm high. This coupled with the height of the new rings would give you back a min of 20 moa (80 clicks) up to 35moa (140 clicks).







PS - Sorry for the late reply to this thread. The weather is playing havoc with my internet connection and i am barely able to get a connection let alone hold it long enough to reply.