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T65

How much off mechanical zero is acceptable.

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Hi Guys

 

I have a scope which has a listed 15 Mils of adjustment. However it has a total travel of 18.6 Mils from left to right. So I would assume its mechanical zero is 9.3. I.e 93 clicks from centre either side. (Not wanting to name the make in case this biases opinion) How much when zeroing the windage would be acceptable for the scope to be offset from mechanical zero. Plus how much error is acceptable for the rings and rail combined. Shooting out to 1100Yards.

Thanks Lee

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Using Burris Signature offset rings, I struggle to get closer than 5 MOA, or 1.5 mils between the scope being centred and the rifle being zeroed.

Regards

JCS

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My pm2 has 60 clicks each way on the turret scale, i’d expect to have at least that.

dont know that i’ll ever use it, but it would annoy me not to have it 

that would do 1000m in a 28mph wind

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My S&B PM11 mounted in Sphur mono mount was 2/10th of a mil off mechanical centre:  ie 2 clicks.  The action is a Barnard PL with a Barnard picatinny rail.

The stacking of tolerances of the fit of the mounts, the mounts themselves, the rail fixing alignment on the action top, the concentricity of the barrel to the action, and finally the internal accuracy of the scope all contribute to the necessary mechanical offset required to bring POI and POA into alignment.

For example: If you have 4" centres for the mounts and 1thou of an inch (less than a fag paper) out of alignment in the horizontal plane that's .25 Mil or 0.84moa windage adjustment (if my maths is up to it).  You can see that tiny mechanical errors quickly build up quite an optical adjustment.

If you are unhappy with the optical zero being well away from the mechanical centre you could try loosening everything and carefully re fitting with nice even take-up of screw tensions etc.  I had a scope "mounted" on a brand new Sako in Optiloc mounts by a well known gun shop in Derby.  It was completely crap - all the mechanical aptitude of a ham fisted ape.  10min in my man-cave and the mechanical zero was not far off the optical zero.  Lesson learned.

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Thanks for the replies. If i can explain some more.

Scopes are fitted using torque wrench and even gaps either side.

The problem I have is that my set up using 3 different mounts are giving me different readings. Using a 1 piece mount the error is 49 clicks left of mechanical centre and 33 clicks left of mechanical centre using 2 different 2 piece rings. If I change the scope. Same make and has the stated 15 mils (150 clicks) the error drops down to 26 clicks left of centre with the 1 piece mount and 9 clicks with 1 of the other 2 piece rings. 

If I change rifles the original scope and 1 piece mount changes to 27 clicks left and the 7 clicks left with the other scope. This repeats its self on the third rifle.

Mounts and rings can only go on 1 way as they have built in bubble levels.

 

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what's the rifle/action and what scope?

Is the ring picatinny or dovetail ?

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1 hour ago, T65 said:

Rifle is a tikka T3 Tac A1 rings and mounts are picatinny.

 

Tikka - Well made rifle with integral picatinny rail.  If I understand your earlier comments: you assume the scope is ok, and you say you've tried another, if so I suspect your rings are not being lined up properly.

I assume you have actually shot this so you know the error is as stated?  If not how are you determining the scope is off axis? 

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Since using Spuhr mounts scopes are zeroed much closer to mechanical zero as before. Two weeks ago I went hunting with Hakan Spuhr, he told me they did tests with scope mounts holding zero in picatinny rails. When mounts of any brand fitted dry to rails the zero holding was not good after an impact. Greatly reduced issues when they mounted well oiled. Makes sense.

edi

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Scopes hold thier zero. So i don't think that is any cause for concern. Interesting that an oiled mount holds better zero.

11 hours ago, Popsbengo said:

Tikka - Well made rifle with integral picatinny rail.  If I understand your earlier comments: you assume the scope is ok, and you say you've tried another, if so I suspect your rings are not being lined up properly.

I assume you have actually shot this so you know the error is as stated?  If not how are you determining the scope is off axis? 

I have shot this rifle and it groups well. The problem is I don't know if I have a compounded problem  with the scope, mount or rail. Zero is being obtained at 50m's not ideal but all I have to work with. Rifles have been zeroed at 200m's before but I did not take the readings.

What I can deduce is  

Tikka

1) With scope 1 and the 1 piece mount.  I have zero at 49 clicks to the left of mechanical zero.

2) With scope 2 and the 1 piece mount. I have zero at 29 clicks left of mechanical zero.

This would seem to indicate that the rail and mount have a compounded error of 29 clicks if the mechanical zeros are true. However this does not explain the extra 36 clicks of scope 1 which should only have 150 and not 186. Plus the mount is machined from a single block so  could this really be out of alignment?

3) With scope 1 and 2 piece rings. I have zero at 33 clicks left of mechanical zero.

4) With scope 2 and 2 piece rings. I have zero at 9 clicks left of mechanical zero.

If I change to 2 different rifles I get the same readings on both rifles.

1) Scope 1 and 1 piece mount. Zero at 26 clicks left of mechanical zero. 

2) Scope 2 and 2 piece rings . Zero is 7 clicks left of mechanical zero.

No here is what really throws the figures out

Scope 2 with 1 set of the 2 piece rings. Zero is 15 clicks right ?? of mechanical zero. 

I can only test with 1 set of the 2 piece rings as one set are to low.

Alls these measurements have been tested twice with same results.

 

 

 

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Have just tried this and when I put the mirror up against the scope it all goes black and I can't see any thing. I don't have illuminated reticles.  

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Have just tried this and when I put the mirror up against the scope it all goes black and I can't see any thing. I don't have illuminated reticles.  

Just tried with a cheap scope and I can just about see the double cross hairs but on my higher mag scopes with the mag turned out it is just black in the centre.

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I have my suspicions what the problem may be but I'll back out now.

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I cant really see the point of this exercise !!!!!

It is what it is.....

What's the most windage you've ever shot with dialled in which may make this relevant 

No I deer 

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11 hours ago, No i deer said:

I cant really see the point of this exercise !!!!!

It is what it is.....

What's the most windage you've ever shot with dialled in which may make this relevant 

No I deer 

The point is I don't know how much windage I may need. Strelok states in a 25mph wind at 90 degrees at 1100 yards I need 6.8 mils left therefor I am 2.4 mils short of adjustment.

Forgive me for not running this question by you before I posted. I now understand if it's not relevant to you then it has no place being asked. 

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🤣😂.

Shooting in 25mph winds from 1000yds is extremely difficult let alone 1100yds 😅.

I've done it once in a club comp and it's a waste of ammo 🌬🌬🌬.

There are plenty of scopes out there that have alot of windage but alot have reticles that will give you the option of an extra 10 plus minutes if you really wish to shoot in such windy conditions..

Good luck with that 👍

No I deer 😁💋

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19 minutes ago, No i deer said:

🤣😂.

Shooting in 25mph winds from 1000yds and its extremely difficult,I've done it once and it's a waste of ammo 🌬🌬🌬.

There are plenty of scopes out there that have alot of windage but Alot have reticles that will give you the option of an extra 10 plus minutes if you really wish to shoot in such windy conditions..

Good luck with that....

No I deer 😁💋

See you can give advice without coming across as a complete 

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29 minutes ago, No i deer said:

🤣😂.

Shooting in 25mph winds from 1000yds and its extremely difficult,I've done it once and it's a waste of ammo 🌬🌬🌬.

There are plenty of scopes out there that have alot of windage but Alot have reticles that will give you the option of an extra 10 plus minutes if you really wish to shoot in such windy conditions..

Good luck with that....

No I deer 😁💋

quite:   😂😂

 

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I have again tried the mirror method seems direct sunlight is better than 2 spot lights. The results are with scope 1 it is perfect both mechanical zero and optical zero are the same. Scope 2 is off by 3 clicks to the right from mechanical zero.
What now comes into play. Is why there is 20 clicks difference in the same 1 piece mount between scopes 1 and 2 if the only error between scopes is 3 clicks right ? Or is there something else that I am not factoring in.

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8 minutes ago, T65 said:


I have again tried the mirror method seems direct sunlight is better than 2 spot lights. The results are with scope 1 it is perfect both mechanical zero and optical zero are the same. Scope 2 is off by 3 clicks to the right from mechanical zero.
What now comes into play. Is why there is 20 clicks difference in the same 1 piece mount between scopes 1 and 2 if the only error between scopes is 3 clicks right ? Or is there something else that I am not factoring in.

Fitting skill?

Just saying

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33 minutes ago, Popsbengo said:

Fitting skill?

Just saying

I must be good if I can get it wrong on all mounts and rings twice. With the exact same results.😄

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I shot this morning on stickledown at 900yds and 1000yds

At 900yds in 10mph and gusting and it was ok and I shot quite well.

Back at 1000yds wind got up more and it was 15mph ish and gusting 20 odd and it was changing through the string of 4 shot taken in around 25 seconds and I couldn't get 4 identical targets,2 or 3 at best,it was basically unreadable, 25mph constant would be not to bad,gusting would be waste of ammo...

I was using my 284 with 180gr scenar l's and i had 8 minutes mean left wind on and aiming off minute plus.that was hard work 😅.

Good practice I guess but I would of rather used the ammo on a better day 😆

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