Rifle Scope: Finding Mechanical Center

[whitefish]

I'm mounting a scope and I was playing with the windage and elevation knobs (I couldn't help myself) .

Anyhoo, I'm trying to reset the scope crosshairs to factory (mechanical) center. In my manual its says to turn the windage and the elevation turrets counter-clockwise all the way, and then back again 1 1/2 turns (1 turn = 34 clicks). In playing with my scope, however, there are exactly 3 turns and 19 clicks range in both the elevation and windage turrets.

My simple mind is thinking, 1 1/2 clicks is not mechanical center. 1 1/2 plus 9.5 (9 or 10, no half clicks) clicks is. Am I missing something here?

[Scorch]

No, you're not missing anything, you're just making the whole process harder than it needs to be. By being close to mechanical center, you should be able to print on paper at 50 yds and adjust from there. Very few rifles will shoot to point of aim with the scope at mechanical center due to differences in harmoonics, variations in mounts, differences in bedding pressure, etc. By getting you close to mechanical center, they are helping you get started in the sight-in process, but you may actually move the crosshairs quite a ways to get the rifle sighted in. Get close to mechanical center and go from there.

[whitefish]

No, you're not missing anything, you're just making the whole process harder than it needs to be.

True enough - however, the last few scope I've mounted have been adjusted to be as close to mechanical zero as possible before adjusting the scope. I've done this by lapping and adjusting the windage screws on my Leupold STD mounts. I haven't had to use shims yet. This is the process recommended by Pentax in their scope mounting guide.

I was just curious as to why the manufacturer would seemingly be that far off in their instructions (1 1/2 turns versus 1 3/4 turns). I was going to mount the scope tonight, but I think I'll give them a call tomorrow to make sure I'm doing this right.

[whitefish]

I heard back from the manufacturer today. As I thought, go through the full range of both turrets counting each click. Then divide by two.

Simple

[Alleykat]

I was just curious as to why the manufacturer would seemingly be that far off

The manufacturer wasn't counting on the newbie's being off his anti-anxiety meds!

[Harry Bonar]

Sir:
Take a carboard box, shorter than the scope - cut two grooves and lay your scope in the groves and rotate it until the crosshairs stay in the same mark on a place on the paper (or some other mark). That will be the optical center.
Harry B.

[user]

When I mount a 'scope, I use a micrometer to make sure I've got the mounts within a thousandth of an inch of each other, from side to side.

[dreamweaver]

I hope this isnt too far off the subject but what about those lasers that you chamber in the gun? Wouldnt that be the most accurate way?

[whitefish]

The manufacturer wasn't counting on the newbie's being off his anti-anxiety meds!

When you pay 2k for a scope, you would think they would get the manual right.

dreamweaver, I've used a laser pen as a bore sighter. My thinking is that if you don't have the laser pen perfectly aligned in the chamber, you won't see a clear red dot on the wall. A chamber laser will give you just that much more acuracy.

I tried using a bore sighter for my last scope mount job, and it was off - way off at the range. The first scope I mounted on my A-Bolt was with a laser pen and it was bang on. I just had to make adjustments for bullet drop.

I'm re-mounting my new scope using the laser pen method, hence the questions on optical center.

[Alleykat]

When you pay $2k for a scope, you'd think you'd "discover" how to remove the bolt and actually sight through the bore.

[Slopemeno]

'zactly how I do it too...

[whitefish]

When you pay $2k for a scope, you'd think you'd "discover" how to remove the bolt and actually sight through the bore.

Nope, I got modern and used a laser.