Bore-sight/sighting in problem:

[Sporting Lad]

I've got a Redfield Revolution TAC (3-9x40) that's served me well across several rifles.
It worked successfully on my Savage 14(sold it) and on my Savage 10 whilst I waited for a Sightron precision scope to arrive. On the '10 I did the 'old school' bore-sight method and got on paper with my first shot, then had a happy time until I replaced it with the new scope.
I then decided to mount the Redfield on my M-14 using a CASM rail. Unable to eyeball a bore site the old way cos of the receiver's design, and unable to have it bore sighted with the 'stick this in your muzzle' thing, cos of the flash hider, I just plunked the scope onto the rings and torqued everything down, hoping to see a hole on paper when I got to the range. I did get on paper, and my windage was near perfect on my 25 yd sight in! But the hole was about 9" high. That means cranking down a lot of clicks. Well, I cranked and cranked until I hit bottom, but the next shots told me I still needed more.
I went home to reconsider how I'd mounted the CASM rail and how I should be able to drop the front a few MOA to gain the down clicks I needed. Meanwhile...

My AR wanted a scope, so I began looking for which scope to put on it.
While I was considering my options, I decided to put the Redfield onto my AR until I got the M-14's CASM rail dialed in. When I did the change-over I needed different (higher) rings. Now we come to the weird(er) part:
The way the AR is designed, it's easy to do the traditional eyeball boresight if you separate the lower, remove the bolt, and peep thru the barrel. I got that all lined up, then I looked thru the scope. The windage was aligned perfectly, but the centre of the reticule was still high compared to the bore. When I tried to crank it down I remembered that it was already down all the way from when it had bottomed out on the M-14--it would not go any lower in the taller rings either.

So "WTF"?
I don't have any reason to suspect that the scope is 'broken'. I'm feeling like there's something really basic that I've overlooked, but my brain is fried. I've mounted lots of scopes before.
Why is the scope doing the same thing on both rifles, each with different rail bases and rings?

The only thing I can think of is that I've never mounted this scope on either of these rifles before--when I mounted it on the Savage 10 I went directly to a 100 yd zero, and was hitting 1 MOA out to 300. With these other two I'm trying to bore sight at 25 yd. (actually it's only 40 feet, or ~15 yd in my back garden). Could that just be too close, as regards the parallax effect?
Should I be out at the range to do my bore sights?

Or am I just cranking the elevation turret down when I ought to be cranking it up? :0 ]
Help me if you can.

 

[icedog]

That's a brain teaser to be sure, but I'm sure it has nothing to do with the shorter distance involved in the bore sight. I have about a 45' look from one side of my living room to the far side of the dining room where my wife has a small collector plate on the wall. I've bore sighted a good number of scopes at home using the details on that little plate and the old "peek down the bore" / adjust the reticle method, with a 100% success rate.

Not sure where to go with the rest of the problem once you're sure it's all torqued down properly. What I usually do before mounting any scope is set the windage and elevation both at mid-point, do my collector plate bore sight, get a hole on paper at 25 yds., then, with the bore in the same position, adjust the reticles so that they are centered on the hole. After that I take a "check" shot to ensure that the bore and crosshairs are properly lined up at 25 yds., then move out to 100 and adjust as required ... not complicated or difficult so long as the bore is OK, and there are no mechanical issues with the mounting.

Hopefully someone else will chime in with other possible options/solutions.

 

[skypilot]

How high was the scope reticle above the target bull when the target bull is centered in the bore?

At 40 ft. And assuming you wish a 100 yd zero you would be close to the scope's height above bore with the reticle and an actual shot impacting about the same distance low.

So if you are currently 3" above bore with the scope, AND scope reticle is 3" above the 40 ft bull, AND with bore centered on the 40 ft bull, you would likely be in the bull at 100 yds with an actual shot, but 3" below crosshair with impact at 40 ft.

If you are way more off than that, it may be the scope. Tac scopes aren't made with a lot of adjustments in Windage or Elevation. You likely have 50-60 moa max end to end, so 25 to 30 MOA up and same down if it centers exactly.

Never had much problem other than with Tac scopes and 20-30 MOA rails. Usually it's pretty straight forward.

 

[Sporting Lad]

What's happening on the inside?

...What I usually do before mounting any scope is set the windage and elevation both at mid-point, do my collector plate bore sight, get a hole on paper at 25 yds., then, with the bore in the same position, adjust the reticles so that they are centered on the hole. After that I take a "check" shot to ensure that the bore and crosshairs are properly lined up at 25 yds., then move out to 100 and adjust as required ...
Hopefully someone else will chime in with other possible options/solutions.

OK, this is very like the method I use as well.
When I was a tank gunner we zeroed the 105mm using the same method with 'cross-hairs' of twine taped to the bore. Look thru the open breach, lay gun on target, then adjust sight onto same POA. Then to live firing range where we did our final sighting in at 1200m. One of the exercises we practiced to use in a combat situation was called "burst on target". If the first round was a miss, we would see the path of the tracer, and usually an explosion near the target. That spot on the reticle (the "POI") is noted and the gun is moved so that that POI is covering the target and the next round is then fired. Scoring a hit meant you were still alive. All good.
But when it comes to a scoped rifle--here is the point where I get confused: Say my grouping is high and to the right. So I'd need to move the elevation turret down ("D" or clockwise) so many clicks and the windage turret left ("L" or clockwise) so many clicks, correct? I know this is fundamental to the whole sighting in operation, but I always have difficulty getting my head around this: What is actually happening to the reticle during all this cranking of turrets?? It is physically being moved down and to the left?
If that's so, then it seems contrary to the idea of getting the reticle "centered on the hole" as you've explained so well, and the 'burst on target' method.
So is "down" really UP? Is "left" really RIGHT? I seem to get this theory backwards every bloody time. I don't notice any apparent movement of the reticle--I just count the number of clicks needed, fire for effect, then adjust using trial and error (mostly error).
I need to write this out in language I can understand for future reference.
Sorry about all this rambling in order to ask a simple question, but I expect I'm not the only shooter who has trouble with this concept. And I hope you can understand my question!

 

[9.3mauser]

But when it comes to a scoped rifle--here is the point where I get confused: Say my grouping is high and to the right. So I'd need to move the elevation turret down ("D" or clockwise) so many clicks and the windage turret left ("L" or clockwise) so many clicks, correct? I know this is fundamental to the whole sighting in operation, but I always have difficulty getting my head around this: What is actually happening to the reticle during all this cranking of turrets?? It is physically being moved down and to the left?

No, if your rifle is shooting high, the reticle must physically move UP, to the point of impact. The dial says "DOWN" because most people find it less confusing to picture the bullet hole being brought down to the aiming point.

 

[Magellann]

If you can look through the scope while you or someone else turns the windage & elevation you can see the crosshairs move in the scope. I have scopes where up moves the poi up, and others where it means the crosshair moves up.
Hopefully this is standardized now between all the scope manufactures.

 

[jjohnwm]

On any scope I've ever used, the Up/Down on the adjustment turrets refers to moving the bullet impact in those directions, i.e. moving the reticle in the opposite direction. If your group is low, you adjust the turret UP until the group and the crosshairs meet. If your crosshairs are looking at a point much higher than the bore is then your group is low; you need to adjust the scope UP. This means that the point of impact and/or place where the bore is pointing will appear to move UP in the field of view, although what you are in actuality doing is moving the reticle DOWN to meet the point of impact.

It's way easier to do it than to explain it. Unfortunately it's also pretty easy to get turned around mentally and screw it up.

 

[Juster]

On any scope I've ever used, the Up/Down on the adjustment turrets refers to moving the bullet impact in those directions,

Exactly right. I wrote an app for that:

You see people going through 10 rounds, and being none the wiser.

 

[Sporting Lad]

Something to remember!

That is so clearly understandable you could have it printed as a poster!
I'd hang it on the wall of my shop; it would save every gunshop staffer untold hours of
'spainin' to folks how to sight in.
I know--I'll make a wallet-size one to carry with me!
thx so much for that learning aid.
You've managed to simplify my life.
A good picture truly is worth 1,000 words!

Cheers,
SL