Scope internal adjustment

S

Stats Shooter

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Typically I mechanically zero my scopes as best I can. I use Burris signature XTR rings with the inserts that have the ability to build in up to a 40 moa offset.

My question is this:
How far from the max/min internal adjustment do you guys like to stay? I have heard if you hit the stops or remain very near the stops you can have issues. I am going to shoot a match in a couple weeks and I have 9.6 MRAD internal vertical adjustment available and typically use 4.4 MRAD to come up from 100 yard to 600 yards. My scope is a leupold Mark AR Mod 1 with 19.6 MRAD total internal adjustment. I'm sure that isnt too close to the stops, and if I wanted to i could cant the scope down another 5 MRAD so I'm not asking for this particular situation. But what if I were using this scope, or any other for that matter, for a longer application? In general, how close is too close before you would want to add more angle to the scope base/rings?
 
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With a good quality optic it probably makes no practical difference how close you are to the adjustment limits.

It's always good to start out as close to the center as possible to allow the most leeway in all directions, but other than that most won't see any difference.
 
Tracking will be most important. If it tracks accurately up/down/over to match the distances and windage needed for your -CENSORED--CENSORED--CENSORED--CENSORED-s, then it shouldn't matter how close you are to the travel limits.
 
Scopes are "tube in a tube" as far as adjustments go. If you can bore sight the scope so that it is very close to mechanically centered you can make the most of your vertical adjustment for dialing in long shots. That is, if you have a scope that you manually dial in for long shots rather than set it at a point blank zero and call good.

The "tube in a tube" description is important, because if the little tube is near the sides front and back, it can't adjust up and down as much. And the opposite is also true.

If you just zero it in at two inches high at 100, doesn't really matter where the zero is with regard to the mechanical zero.

Jimro
 
.jmr40: Unless you are using windage adjustable mounts doing this is a complete waste of time.
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^^^^^^Huh?
I'm shooting in some medium / long range matches. I'm asking if/how much, getting close to the stops with respect to internal adjustment affects the scope. I'm not sure what you mean? Because making sure you have enough internal adjustment to go from shot range zero to long range zero by adjusting the base isn't a waste of time
 
. If you can bore sight the scope so that it is very close to mechanically centered you can make the most of your vertical adjustment for dialing in long shots.
/QUOTE]

For long range, you're better off not being mechanically centered for elevation. Much better to have a substantial down-angle mount leaving a 200 (or 100) yard zero near the "down" limit- leaving most of the total travel available for "ups". This way a scope with as little as 30 or 40 minutes of total travel can be used when it would otherwise be inadequate.
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Tobnpr,

That is kind of what I did....i didn't go all the way down, but I left myself with enough vertical adjustment to go from 100 to 900 yard zero....i could add another 5 MRAD, still not be too close to the bottom, and be able to go from 100-1000 yards
 
tobnpr,

Allow me to explain further because I must not have been clear enough the first time, specifically because I chose not to address offset rings or bases in that answer.

Mechanically centering your scope allows the maximum elevation adjustment because the inner scope tube isn't going to hit the outer scope tube until it is at the mechanical maximum. With a scope that has 80 minutes of vertical adjustment, you only get half of that for "come ups" but you get even less if your zero requires 20 minutes of horizontal correction.

If you are 20 minutes to the side, or half the absolute distance for horizontal adjustment, now the inner tube can only drop down 20 minutes before it hits the outer tube.

If you use an additional vertical offset base, like the common 20 minute rails, then your 80 minute scope can now give you 60 minutes of come up IF you mechanically center the horizontal adjustment. If you don't, and you use 20 minutes of horizontal adjustment to get zeroed, now you are back to 40 minutes of come ups, the same as if you used a zero degree mount with a mechanical zeroed zero.

So my previous answer is still valid, you get the most possible adjustment from a mechanical zero in the scope. You can get more adjustment when you start using external adjustments like offset rings and bases (or external adjustments as used on old Unertl scopes). But that is the difference between internal adjustment and external adjustment, you don't run into an extra outer tube when using external adjustments.

Jimro
 
Ahh, I see what you meant Jimro,

And I did mechanically adjust my windage also (+/- 1 moa) to get it very close to the the middle.
I use Burris signature rings XTR rather than a 20 moa base. That way I can cant the inserts for elevation AND windage.

Of course I cannot get the windage perfectly zero mechanically because different bullets will have +/- an inch or two different impacts at 100 yards, but very close to the middle.

But I can see what you mean, since it is a tube within a tube, if you are pegged near the edge on windage for your zero, then because it is round, you will contact the upper limit sooner.

Great point that I didn't get at first
 
Mississippi,

Sounds like you've got a good setup for dialing in some long range shots.

I don't worry about small windage adjustments either, the vertical loss is very very small when the windage deviation is small.

Good luck reading the wind!

Jimro
 
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