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Old 26th May 2014, 07:00 PM
Arthur Arthur is offline
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Join Date: May 2014
Location: North West
Posts: 11
Question Scope mounts - optical centres - confused

I have an MTC Viper 10x44 scope mounted on an AA S200. having sorted out the trigger I decided to have another look at the scope mounting, eye relief etc.

I read about the 'optical centre' and being a photographer I thought it sounded interesting and I'd look at it.

On this scope there are 13 full revolutions of the turret to go from far left to far right, so I went to one end of the travel and dialled back 6.5 turns to put the optics in the centre. (Vertically there are 10 full turns of the turret.)

I am not sure that this is a valid way of finding the centre(?) but anyway I read it on the internet so it must be true.

I lined the rifle up on a rest on my indoor 13m range and fired off a group that was a bit low and around 9cm to left.

On a whim, I reversed the mounts i.e. the allen bolts of the mounts were on the right, I spun the mounts round 180 degrees and mounted everything exactly as it was but with the allen bolts on the left. Shot a group and the group was still a little low and now 4cm but still to the left

Swapped the mounts back round: a little low and around 9cm to the left.

Swapped the mounts back again: a little low and 4cm to the left.

I checked that there was no way I could replace the barrel cock eyed after having sorted out the trigger, but no it's fool/me proof.

I left it that way round and zeroed in, shoots fine at 13m and I'll try it at different ranges when I can.

But why oh why that particular difference in poi from turning the mounts around? Other than rails and barrel not being parallel I can't deduce how that reproducible difference would happen?
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