Thread: Shimming scope...

I fitted a Nikko Panamax scope to a JW-15.

At 100m it is shooting about 20cm low with scope cranked right up.

I'm a noob at this stuff. I'm assuming that I need to shim the rear mount to provide some lift?

My concern is that if the rear mount is higher than the front, does that not potentially put some strain on the scope tube?

Or is there another way?

You don't need to shim them much to get the change you are looking for.

Shimming the rear ring is OK and will not cause problems. You can cut shims from aluminium drink cans with a pair of scissors. The shim only needs to be at the bottom, about15mm is long enough.

I shimmed the rear mount between titanium action and under the mount base with cut bits of beer can did not take much on my 7 mm WSM and DNZ scope mount as my Swarrrovinsky Z8i did not have enough adjustment.

My rifle is a Browning Mountain Ti I could not get a 20 moa mount anywhere.

It might have been three thicknesses of beer can this then put my rings out of line so I went to the local engineering shop and purchased a section of 30 mm diameter finished bar $5.00 which with lapping compound I trued the bottom half of the rings so there is no bending stress on the scope tube.

If you can do the mathematics you could work out the thickness you need I personally did it trial and error so my scope gave me 3/4 elevation and a full turn on the Svarovvvaskiee target style turret with some to spare so I am never near the maximum travel in the turret adjustment.

At 100 yard zero my scope is 1/4 travel up from maximum down.

All very cheap and works 100%

Originally Posted by xtightg

I trued the bottom half of the rings so there is no bending stress on the scope tube.

Yep, that's the way I'd do it. I check ring alignment and lap as required for every scope I mount, but especially if you're deliberately offsetting the rings. The gear is cheap and the process is quick, well worth it in my opinion. My lapping rod is a piece of 25mm cold-rolled, I stick 600gr wet and dry sandpaper on it with spray adhesive which brings it almost perfectly up to 25.4mm. I've tried lapping compound - the 600gr paper works better in my experience.

These are cheap rings (although look better than the rings it came with) so will try the swapping back to front / turning rings thing and see if that makes a difference.

I have a shim(s?) that came with some Talley rings for my 308, might see if those will work.

Edit: Although any excuse to drink beer. Waikato cans better than DB Export Gold?

Why don't you just get some weaver tip offs for 30 odd dollars

Originally Posted by Russian 22.

Why don't you just get some weaver tip offs for 30 odd dollars

What's the advantage of the tip offs?

Now's the time to probably ask:

One of the rings has a grub screw set into the base of the ring, that would contact with the dovetail rail.

What's this for? Could I screw it out slightly to get the raise that I'd like? I assume I'd have to thread-lock it to stop it unscrewing itself?

Originally Posted by mimms2

For all the massive recoil. Mostly seen on airgun rings, IME.

Yep, sounds like a recoil lug, it should screw out. You don't want it if you don't have the hole in the dovetail for it to sit in. It might be the cause of your scope problem.

Originally Posted by Cigar

Yep, sounds like a recoil lug, it should screw out. You don't want it if you don't have the hole in the dovetail for it to sit in. It might be the cause of your scope problem.

It's in the rear ring, so would be helping if anything. But it was retracted,so shouldn't be causing any issues.
Will remove it tho, just in case.

you can buy shim metal from acorn models in chch

https://www.acornmodels.co.nz/

various materials various gauges

Originally Posted by davetapson

What's the advantage of the tip offs?

You shouldn't need any shims or ghetto bubba work

Originally Posted by davetapson

I fitted a Nikko Panamax scope to a JW-15.

At 100m it is shooting about 20cm low with scope cranked right up.

I'm a noob at this stuff. I'm assuming that I need to shim the rear mount to provide some lift?

My concern is that if the rear mount is higher than the front, does that not potentially put some strain on the scope tube?

Or is there another way?

The JW 15 factory mounts are a bit...temperamental. I managed to fit a scope to it that on first install had a conflict between zoom ring and bolt handle when the bolt was pulled back - turned one mount round 180deg and scope now barely interacting with bolt. It may be the same if you swap the front and back mounts with each other. And bore sight, as in, bore sight, no fancy laser needed.

Originally Posted by davetapson

I fitted a Nikko Panamax scope to a JW-15.

At 100m it is shooting about 20cm low with scope cranked right up.

I'm a noob at this stuff. I'm assuming that I need to shim the rear mount to provide some lift?

My concern is that if the rear mount is higher than the front, does that not potentially put some strain on the scope tube?

Or is there another way?

A couple of questions... Why 100m? Most will sight in 22LR for 50 or 75 metres. Reason being if you are zero'd at 100m then you are likely to be fairly high in the middle at around 50m. Enough to go right over mr rabbits whole body. I usually zero mine at 25m with subs. This puts them about 1"high at 50m and about zero again at 70m and about 5 to 8 low at 100m depending on the ammo. If you are zero'd at 50m there is a fair ole bit of drop at 100m. More than most would think.

If you do really want it zero'd at 100m , then as Gundoc said, "Shimming the rear ring is OK and will not cause problems. You can cut shims from aluminium drink cans with a pair of scissors. The shim only needs to be at the bottom, about15mm is long enough. "

And the recoil lug screw in the bottom is harmless if left in there. usually it will be screwed down into a hole or groove on air rifles as the spring recoil vibrations on those are savage on scopes. I usually leave them in there. Otherwise they get lost and one day you may need it.....