rear sight mechanical zero and index lines

[shamrocks]

I have never paid much attention to this before but I wondered about this. On the rear base of the carbine's adjustable sight there is a single index mark that lines up with any of several lines on the adjustable part of the sight and is held in place by a tiny screw. I was going to set my mechanical zero by moving sight all the way to left, then count clicks all the way to the far right and divide that number in half to move the required number of clicks back to the center. Now, when that is done the index lines from the base and movable portion are not lined in the center...the line on the movable portion are a bit to one side of the base index line. Should I loosen the screw in order to adjust the small movable index marks to align with the base's center index line and will that then be proper mechanical center? Hope my question isn't too confusing.

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[jimb16]

Yes. That will allow you to compensate for high wind then be able to move the sight back to zero when you don't need the windage.

[shamrocks]

Thanks, I thought so but wanted to be sure.

[emmagee1917]

Ummm , I'd say no.
In an ideal world the "mechanical " center and the actual hitting center would be the same . This is not an ideal world. Start with your mechanical center and sight in with actual shooting on a windless day. Zero your rifle in . Move your plate to align with your true " no wind " center line. Now you can return to the no wind zero of your rifle any time and make proper dope adjustments for the weather from a known point.
This is an advantage over the other adjustable style sight or the Garand sight where you have to keep track of how many clicks left or right you need for a windless day then adjust your dope from there. Of course , the disadvantage is if your screws loosen up , you've lost your place.
Chris

[browningautorifle]

Chris is right. The index is to show when the sight is zeroed and at center. Then you can adjust off for wind and find zero again because you have the scale. Zero the carbine and slip the scale to show as centered.

[shamrocks]

Chris is right. The index is to show when the sight is zeroed and at center. Then you can adjust off for wind and find zero again because you have the scale. Zero the carbine and slip the scale to show as centered.

thanks, that clears up some other advice from a source and makes perfect sense so that you can always find zero again if you have to make windage adjustments later on.

[INLAND44]

Okay, when the sight was installed, the aperture was pretty much centered. Then the sight base was drifted in the dovetail to correct alignment while shooting inside a building with no wind. Then the sight base was staked in place without regard to the mechanical center of the carbine. Having a rear sight centered in the receiver is uncommon. On early adjustable sights, there was a movable index with a screw for making fine adjustments from the factory setting to account for different ammo, conditions, etc. One would never arbitrarily make an adjustment to the aperture or index plate just to line it up with the 'mechanical center' of the sight base unless the sight were going to be installed on a carbine and the sight base drifted into alignment during firing. If you have to put a click or two into the adjustable sight to zero, the index plate should have sufficient travel to then be re-aligned to center. That is with a properly-installed sight base. A properly-installed and aligned adjustable sight should have the aperture at or near the center of the sight base so fine adjustments will be within the range of the index plate, and also so the range of movement of the aperture is at it's maximum to each side.
On this one the aperture is a little left of center but the index plate could accommodate the shift. Also, the whole sight base is drifted a little left for the gross alignment adjustment.

[browningautorifle]

Well, to be exact, they didn't drift anything. There's a tool for it. And it's here... Rear Sight Removal Tool with or without part number Sounds like you found a more complex way to say it...

[bonnie]

shamrocks,
My closeup vision is fading and I find the small windage marks on the rear sight hard to see without reading glasses, even after filling in the marks with white paint.
After zeroing and getting the windage marks lined up on the rear sight, I also add two small dots of paint. One on the windage knob and one on the right side wing of the rear sight. A quick glance tells me if both are aligned the rear sight is zeroed. Helps when shooting a match.

[shamrocks]

shamrocks,
My closeup vision is fading and I find the small windage marks on the rear sight hard to see without reading glasses, even after filling in the marks with white paint.
After zeroing and getting the windage marks lined up on the rear sight, I also add two small dots of paint. One on the windage knob and one on the right side wing of the rear sight. A quick glance tells me if both are aligned the rear sight is zeroed. Helps when shooting a match.

thanks, that's not a bad idea at all