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Thread: Shimming scope...

  1. #16
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    Quote Originally Posted by davetapson View Post
    What's the advantage of the tip offs?
    You shouldn't need any shims or ghetto bubba work
    Dead is better likes this.

  2. #17
    Member Cordite's Avatar
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    Quote Originally Posted by davetapson View Post
    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.

  3. #18
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    Quote Originally Posted by davetapson View Post
    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.....

  4. #19
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    Quote Originally Posted by timattalon View Post
    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.

  5. #20
    Member zimmer's Avatar
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    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.

  6. #21
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    Shim the rear ring 5-10 thou should get you where you need

  7. #22
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    Quote Originally Posted by rambo-6mmrem View Post
    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?

  8. #23
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    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

  9. #24
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    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.
    davetapson and mimms2 like this.
    If power matters, recoil will be a necessary evil

  10. #25
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    Quote Originally Posted by winaa View Post
    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.
    This is a good. point. A duplex reticle offers 3 vertical aiming points. Normally this lines up well with .22 slug guns. I'm just trying to think the distances that your average 4x scope would lone up with 22lr
    Diligentia Vis Celeritas
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  11. #26
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    Quote Originally Posted by davetapson View Post
    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.....

  12. #27
    Just like Mimms the First
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    Transonic range on 22LR is usually 120-130m.
    Obviously not an issue with subs.
    Diligentia Vis Celeritas
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  13. #28
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    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
    Last edited by Dead is better; 02-03-2020 at 06:52 PM.

  14. #29
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    Quote Originally Posted by Dead is better View Post
    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!!

  15. #30
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    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.

    Sent from my Nokia 7 plus using Tapatalk

 

 

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