Thread: Shimming scope...

Originally Posted by timattalon

A couple of questions... Why 100m?

Basically so I can shoot on the NZDA 100yd range.

Being a city dweller, I don't have the option of choosing my target distance unfortunately, and I have no farming buddies within easy reach for an afternoon's plinking.

I want to practice hunting shooting stances and can't do this on the 25m range and don't particularly want to do it all in .308 on the 100yd range.

Maybe what I should do is zero it at the 25yd range and then just set up two targets at 100yd - one to aim at, and one at point of impact. After all, all you are really looking for is grouping size.

Maybe just put a bright point of some kind on the top of the target frame (1" orange sticker?) to aim at and a target at an appropriate distance below that to catch the bullet strike?

Save me bending my scope for no good reason.

Thanks for asking the question.

Rough cals, also guessing how far apart your rings are.
You say you have maxed out at 20cm low, therefore you need to correct by say at least 250 mm otherwise your windage adjustment could be affected by the curve in the tube.
For 250 mm you will need to shim the back ring by around 11 thou/0.28 mm. Again, I am guessing your rings distance apart.

Now, to go against opinion, I never recommend shimming. Yeah, there's many examples across the net of people doing it. It may be OK on a cheapish scope but I wouldn't ever entertain it on a valuable scope, and I would never do it on a centre fire which yours is obviously not.

Best to try and find the cause first as suggested by others - swap rings back to front, turn them 180 degrees. Try another set of rings.

Of cause there is still the chance the the barrel is so poorly aligned with the action that the rings are not the issue but for some reason barrel alignment issues are usually the barrel pointing sideways.

Shim the rear ring 5-10 thou should get you where you need

Originally Posted by rambo-6mmrem

Shim the rear ring 5-10 thou should get you where you need

5 thou won't be enough, wI'll only raise abut 110 mm. Have done the calculation?

Personally id but a set of burris zrings with a +.020 insert in the rear and a -0.20in the front
But those are almost half the cost of a jw15
So a peice of coke can in the rear ring will have to do

I find it strange you can't dial out to 100m I do it all the time from a 40m zero and it's only 8.4moa using CCI STD's which most scopes should be able to do. I'm only using a vortex diamond back.
As others have said check out your rings swap them around etc. If this doesn't work a cheap work around you can try is to sight in on the top of lower post if you have a duplex reticle. This will give you a little more elevation and if your lucky the center may be close to 50m, worth a try.

Originally Posted by davetapson

Basically so I can shoot on the NZDA 100yd range.

Being a city dweller, I don't have the option of choosing my target distance unfortunately, and I have no farming buddies within easy reach for an afternoon's plinking.

I want to practice hunting shooting stances and can't do this on the 25m range and don't particularly want to do it all in .308 on the 100yd range.

Maybe what I should do is zero it at the 25yd range and then just set up two targets at 100yd - one to aim at, and one at point of impact. After all, all you are really looking for is grouping size.

Maybe just put a bright point of some kind on the top of the target frame (1" orange sticker?) to aim at and a target at an appropriate distance below that to catch the bullet strike?

Save me bending my scope for no good reason.

Thanks for asking the question.

Fair enough. If you are looking to practise so when you use your 308 at 100m you will be a better shot, then you can use the 22 at 50 and use smaller targets.

The travel time is determined by velocity and handily enough the 22LR supersonic are usually around 1300-1400fps and centrefire is usually around the 2600-2800fps whch is about double. As a basic rule of thumb, if you want to practise centrefire and use a 22 practise at half the distance. there are other factors that come into play but as a simple start it works.....22LR at 100 does have an issue with groups as it goes transonic before then and the wobble from that can screw groups up. Subs or target ammo is better for that but being subsonic to start with the drop is horrendous at 100m.I also shot 100m at the NZHA with a 22LR but found aiming at much smaller targets and setting up for 50m gave a better result after practising. (Even allowing for the distance.)
@mudgripz could be worth a chat to as he is well versed in the fine art of 22LR.....

There's also an FX adjustable mount for about $150 at last count. Not centrefire recommended but for a .22 its born for it.

https://www.airgundepot.com/fx-airgu...-dovetail.html

Originally Posted by Dead is better

There's also an FX adjustable mount for about $150 at last count. Not centrefire recommended but for a .22 its born for it.

https://www.airgundepot.com/fx-airgu...-dovetail.html

Those are nifty. More than half the cost of the rifle!!

So it all might become a little clearer. Swapped the mounts around and instead of having a gap between scope and barrel, no gap.

So the mounts are not the same height. There is .2mm diffs in the bases, but dove tails sit on the feet of the clamps, so who's to know.

Considering grinding down the feet of the front clamp by .1mm and hopefully get some play whilst maintaining some clearance.

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