Optical zero

[Snuby642]

Brain freeze.

Bore sight kit MIA.

Scope with 110 moa adjustment, so 55 moa from bottom out without a zero stop would be optical center?

If same scope is on 20 moa rail then would 35 moa from bottom be the new optical center?

My head hurts from looking for my scope kit that's about 3 counties away at the moment I think

 

[Trigger Monkey]

55 MOA up and down would be mechanical center, not necessarily optical center. Instead of doing mathematical loop de loops, why not just pull ye old bolt out of the rifle, look down the bore, and bore sight the old fashioned way?

 

[Snuby642]

I may have to but my eyesight is not the best anymore.

I guess I should reword that to say optically aligned with the plane of the bore? Or is that not really the case?

I have been using my little bore sight kit for so long I can't even remember last time I went old school on it. Probably why I bought a kit. Lol

Not as easy to see through the receiver. And the mounting is probably temporary, not the way I like but parts on hand.

 

[wpeach1912]

Bore sight it as best as you can then just start close range. Like 25 or 50 yards. Even better set a tripod up with your spotting scope on it and have a spotter watch or film with your camera through it to see where you hit. The whole Optical center/mechanical thing probably won’t get you much

 

[Trigger Monkey]

Optically aligned with the plane of the bore? I haven't heard that one before, do you mean bore axis? Or, are you trying to describe optical center vs mechanical center? I don't know.

Mechanical and optical center have nothing to do with the bore, bore sighting, or a relationship with the bore axis, either can be found independent of the optic being mounted. Mechanical center is as discussed, it's the point at which the elevation and windage adjustments are centered within their respective travel limits. 100 MOA total elevation and windage adjustment would give a mechanical center/zero of 50/50 and 50/50. Optical center is a little different and it's the point where the reticle's center will appear to stay stationary when the scope is rotated about its axis. This may not equal mechanical center, it could be that in relation to mechanical center, the optical center of an optic is more like 52/48 and 53/47.

Most optics companies ship scopes optically centered because it's fast and easy to do and is relatively close enough to mechanical center for a user to get boresighted and zeroed without too much effort.

If your eyes aren't as good as they used to be, get the scope back to a center, dial down about six mils/20 MOA from there, and start out at close range to get on paper and push out from there.

 

[Wormydog1724]

I’ve seen someone put a mirror against the lens of the scope, can’t remember if it was the ocular or objective, and then looking through the other end, two reticles will be seen. Turning the turrets allow them to line up, I’m assuming this is mechanical center. I’ve looked through optics with a mirror and saw the two reticles but never tested if it was mechanical center or not.

 

[Trigger Monkey]

Here's a couple videos that go into finding optical center.

 

[Snuby642]

It just has to be close enough not to send something over backstop.

My son got this cheap from someone that ended up needing mils. Then he needed mils. Lol

I can run either and on a fixed distance think the moa has a finer adjustment. End goal 2 inch target at 500 yards.

Yes with an ar 223 I built up.
It's just a goal I have.

 

[Trigger Monkey]

End goal 2 inch target at 500 yards.

In Texas?

 

[Snuby642]

@Trigger Monkey
Didg Ding you got it.

Want to take the challenge on the Black Jack rack. Looks like most guys that are up on the board with ar's are shooting 6 arc and 6 br and it's a challenge to see if I can do it with 223.

I have another 20 inch upper with a bad 6.5 Grendel barrel extension and can replace it or change to 6 arc. Same brass just need new die and has a way better bullet selection.

Had hoped that 69g smk's were going to work but having some problems with practice rounds.

Any suggestions will be welcome.

 

[Terry Cross]

I may have to but my eyesight is not the best anymore.

Just a reminder, light is your friend. You will get the most performance out of weak eyes when there is plenty of illumination so the rule of the day would be to try it outside on a sunny day.

Not as easy to see through the receiver.

Easy peasy.
Split your upper off, yank your BCG and throw your scoped upper across a Fortune cookie of other bags.
Find something small (eyes work exceptionally well with circles) and with good contrast downrange and center it in your bore.
Chase it with your reticle.

Everybody does this all the time even with irons, RDS and scopes going on ARs.