Rifle Scopes Turret adujstment - greater than MOA- what do I do

[wadcutter]

I have a scope that seems to be giving me more than the 1/4 MOA per click. If I dial up 30 MOA at 1000 yards I actually get about 32 MOA and the bullets land too high.
I get about the same % error at other distances as well.

Whats the best way to work around this problem?

 

[Sleeper]

Re: Turret adujstment - greater than MOA- what do I do

What type of scope? Some brands just are not repeatable and are better used in other applications than precision long range rifle. If it is high-end send it for repair. Would you use a set of precision calipers that weren't correct? A scope is the same!

 

[doc76251]

Re: Turret adujstment - greater than MOA- what do I do

If the scope tracks reliably but in adjustments other than advertised it can be used simply by applying a multiplication factor to the ballistic data.


Example: If you observe your scope to adjust 9.25” instead of 10.47” when checking for 10 MOA of movement.

Divide 10.47 by 9.25 = 1.13

Multiply your ballistic calculations by 1.13 and carry on smartly.

Cheers,

Doc

 

[Sleeper]

Re: Turret adujstment - greater than MOA- what do I do

doc, I agree with the math. I just think it depends on the scopes use. Maybe fine for F-class, prob not so good for tactical comp.

 

[Lindy]

Re: Turret adujstment - greater than MOA- what do I do

Take Doc's advice.

I had a chat with a sales representative of a major scope manufacturer recently, and he said the industry standard for error in scope adjustments was 2%, and as Doc knows, a lot of them don't make it.

Most scopes are probably a little off. That's why I always check every scope using this technique.

 

[Lindy]

Re: Turret adujstment - greater than MOA- what do I do

Several ballistic programs allow you to enter the actual adjustment rather than the nominal adjustment into the program. But the errors in adjustments I've found are always small enough to do the math for long distances in my head.

And if you're not taking into account the variation in muzzle velocity of your load with temperature, it's a complete waste of time to even consider the error in scope adjustment.

The art of the precision rifle is based upon making distinctions between what does and does not matter to the objective of hitting targets at long distance.

 

[One-Eyed Jack]

Re: Turret adujstment - greater than MOA- what do I do

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Wadcutter</div><div class="ubbcode-body">I have a scope that seems to be giving me more than the 1/4 MOA per click. If I dial up 30 MOA at 1000 yards I actually get about 32 MOA and the bullets land too high.
I get about the same % error at other distances as well.

Whats the best way to work around this problem? </div></div>
How did you determine the actual elevation change at 1000 yards? Often there is some confusion between MOA and IPHY (inches per hundred yards), which amounts to almost 5% (1 MOA = 1.047 IPHY). If you're acutually measuring IPHY and the scope is really in MOA, note that 30 MOA = 31.4 IPHY.

 

[Lindy]

Re: Turret adujstment - greater than MOA- what do I do

Maybe, but most errors run the other way, when people think they have an MOA scope, but it's actually IPHY.

 

[One-Eyed Jack]

Re: Turret adujstment - greater than MOA- what do I do

But Wadcutter is in Australia, so it's just the opposite.

 

[Rafael]

Re: Turret adujstment - greater than MOA- what do I do

LOL

 

[wadcutter]

Re: Turret adujstment - greater than MOA- what do I do

The scope is a Clearidge 2.5-12.5x42 ultra xp5 with mil dot reticle and MOA turrets.

 

[One-Eyed Jack]

Re: Turret adujstment - greater than MOA- what do I do

Wadcutter, you didn't mention how you came to the conclusion you described in your first post. The Clearidge scope is probably has a second focal plane reticle.

http://www.clearidgeoptics.com/Default.aspx?act=pro&opt=detail&id=841

If so, you must measure angular subtensions at a specific magnification (often it's at the highest mag). If the magnification is high by 5% from the specified value, then your clicks will seem 5% too large.

 

[wadcutter]

Re: Turret adujstment - greater than MOA- what do I do

Jack,
Yes it is a second focal plane scope.
I have got the idea that the elevation turret adjustment is not accurate in MOA by the actual results that I am getting from the group centres at the various ranges that I shoot.

The bullets are landing just too high for it to be due to any other reason that I can come up with.

I dial up for my shots over known distances and the rifle consistently shoots high. This is taking atmospheric conditions into account.
Saturday I sighted spot on at 100 yards, It was then shooting about 45cm high at 1000 yards and over 30cm at 600 yards.
To get the rifle to shoot this flat, my velocity would have to be out by a long way.
I am shooting a .338WM @2652fps with Hornady BTHP match projectiles.
temp 19C 1000mb.
Maybe Im missing something?

 

[Lindy]

Re: Turret adujstment - greater than MOA- what do I do

It's easy to check what the scope is actually dialing.

Put up a big target, say 1.5 meters, at 100 meters, if that's your zero range.

Put an aiming point at the bottom of the target. Fire a couple of shots at it.

Crank on the elevation it takes to get you to a long distance - say 35 MOA. Use the same aiming point at the bottom.

Fire a couple more shots at it.

Measure the difference, and see what the scope is actually dialing.

Or do this:

Optically Checking Rifle Scopes

<span style="font-style: italic">There is no need to guess what the scope is dialing.</span> Measure it.

 

[wadcutter]

Re: Turret adujstment - greater than MOA- what do I do

OK, I went out and checked the scope on a large sheet of paper at 100 yards, the paper was marked in MOA increments up to 35 MOA. i.e. marks at 10.47inches apart @100yards to give 10 MOA points. Also half marks for 5 MOA spacings.
I held the rifle steady in sand bags while another person dialed the elevation turret up and down.
We repeated this quite a few times and got the following average results.

It seems to be out by about 8% This seems to be very consistent accross the entire adjustment range.
i.e. 10 MOA dialed gives almost 11MOA of actual movement. 20 MOA dialed gives about 21.5MOA of actual movement and 30 MOA dialed gives a bit over 32 MOA of actual movement.
Also the 10 power setting that is maked on the power ring for use with the mil dots was out a bit. The scope had to be on 9.5 power for the mil dot spacings to be correct.
What now?

 

[Lindy]

Re: Turret adujstment - greater than MOA- what do I do

Well, if it's consistent, as you say, you just know that you have to reduce whatever a ballistic program calculates that you need to dial by 8 percent. As long as it's consistent, it doesn't matter.

It also helps to be consistent in keeping your dope one way or the other, but not both. To avoid confusion, and also aid you should you acquire a scope with more accurate adjustments, I recommend that you keep your dope in actual MOA, if you're using a ballistic program, rather than what the scope is dialing, but that's up to you.

If you're not using a ballistic program, though, you might just as well keep your dope in what the scope is dialing. Just remember that you may need to adjust that dope if your get a different scope.

And I'd mark the power ring at the point where the reticle is correct.