View Full Version : MOA value of LaRue BUIS
Alpha Sierra
08-01-07, 19:25
I've searched and did not find.
Does anyone know what is the MOA/windage click value of a LaRue BUIS? I got mine today and need to hit the range tomorrow or Friday to zero it up.
BTW, I just keep being impressed by LaRue products and service.
When I bought my M68 CCO mount that's all I got. But today they more than made up for it with a LaRue hat, 'dillo, and little vial of machine gunner's lube!
What length gas system? Are you using a regular front sight tower, or a flip up front sight?
Alpha Sierra
08-01-07, 20:10
What length gas system? Are you using a regular front sight tower, or a flip up front sight?
Thanks for trying to help but none of those factors are relevant to the question as they do not affect the distance that point of impact is moved by each windage click.
Thanks for trying to help butnone of those factors are relevant to the question as they do not affect the distance that point of impact is moved by each windage click.
I'm pretty sure gas system length does if the windage screw is the same pitch between rifle and carbine length. On the carbine length system it would move it a greater angular distance. Or for example, if one click moves the sight .005" laterally, that .005" movement will result in a greater angular displacement on the shorter sight radius.
I'm thinking it's between 1/2 and 1 MOA per click, IIRC.
Alpha Sierra
08-01-07, 20:29
I'm pretty sure gas system length does if the windage screw is the same pitch between rifle and carbine length. On the carbine length system it would move it a greater angular distance. Or for example, if one click moves the sight .005" laterally, that .005" movement will result in a greater angular displacement on the shorter sight radius.
I'm thinking it's between 1/2 and 1 MOA per click, IIRC.
It's actually sight radius, not gas system length that affects the exact click value. And the type of FSB matters not at all.
In any case, the change in actual click value due to the difference in sight radius between a rifle an carbine is not going to amount to 1/10 MOA.
I just need to know the nominal click value in MOA for a LaRue BUIS.
Like I say, it's somewhere between 1/2 and 1 MOA. I know if you have a good iron zero you can get a red dot pretty close by adjusting the dort to line up with your irons, maybe you could do the reverse.
If you have an optic, zero it first. Then install the BUIS and align the windage to line up on the same vertical plane. As long as your cheekweld is good and you've got the dot centered I would think you ought to be close. I can't say for sure though, I got my BUIS before my EoTech so I adjusted the EoTech to line up with irons.
Alpha Sierra
08-01-07, 20:53
Thanks jmart.
My Aimpoint is already zeroed. The BUIS is new to replace a MI flipper that fell apart. I'll just walk the rounds in at 50 yards. I suspect that if LaRue uses a GI windage leadscrew it will be a nominal 1/2 MOA.
Not to be a smartass but why don't you shoot a group at 100 yds, move it a click or two, measure, then determine what the click value is. Let us know. I'm curious myself.
Alpha Sierra
08-01-07, 22:24
Not to be a smartass but why don't you shoot a group at 100 yds, move it a click or two, measure, then determine what the click value is. Let us know. I'm curious myself.
Not a smartass at all.
I plan on doing just that but at 50 yards to make sure I'm on paper somewhere.
The reason I ask is because all adjustable sights (like scopes) have a designed nominal MOA/click value and knowing that makes for a more efficient zeroing process.
Wayne Dobbs
08-01-07, 23:25
Why don't you call LT and ask them what the click value is on their product?
AR15barrels
08-02-07, 01:32
I just need to know the nominal click value in MOA for a LaRue BUIS.
You can't have a nominal click value in an iron sight when you don't know the sight radius.
If you ASSUME (we all know what that means) the sights are for use on carbines, then maybe they were made for some specific MOA on carbines.
Of course using them on a mid-length or rifle length front sight placement would change the value per click by enough to matter.
Why don't you call LT and ask them what the click value is on their product?
No one uses a phone anymore, and that'd be WAY too easy...
SinnFéinM1911
08-02-07, 13:32
Thanks for trying to help but none of those factors are relevant to the question as they do not affect the distance that point of impact is moved by each windage click.
The length of your gas system and bbl are completely relevant. Try measuring a M16A4 bore to FSP and then try it on a carbine... Its different, so then in fact the adjustments are different (not by much - but they ARE)
B
Wayne Dobbs
08-02-07, 14:42
Per Austin at LT, the nominal click value of their BUIS is 1/2 MOA. Obviously sight radius will affect that value, but that is the nominal value of the unit.
Moving on to sports and weather after the commercial break...
Per Austin at LT, the nominal click value of their BUIS is 1/2 MOA. Obviously sight radius will affect that value, but that is the nominal value of the unit.
Moving on to sports and weather after the commercial break...
But what's the MOA value at 200 yards?
Alpha Sierra
08-02-07, 18:46
But what's the MOA value at 200 yards?
1/2 MOA is 1/2 MOA at any distance. The linear distance subtended by that arc varies according to this proportion: 1 MOA = 1" per hundred yards. The actual value is 1.047 inches but such precision is not necessary.
1/2 MOA subtends 1 inch at 200 yards.
Alpha Sierra
08-02-07, 18:48
The length of your gas system and bbl are completely relevant. Try measuring a M16A4 bore to FSP and then try it on a carbine... Its different, so then in fact the adjustments are different (not by much - but they ARE)
B
Yes. I was just asking in practical terms.
Even when I shoot mid range prone matches, I don't calculate the exact MOA value of my rear sight. It is a nominal 1/4 MOA sight and I click as if it were even though my rifle's sight radius may not be exactly what the sight was regulated for.
That was my only point.
Alpha Sierra
08-02-07, 18:48
Per Austin at LT, the nominal click value of their BUIS is 1/2 MOA. ...
Thank you. I had a very busy day at work and did not have the time to make too many phone calls.
Wayne Dobbs
08-02-07, 20:24
You're welcome. Gave me an excuse to speak to a buddy of mine at LT and to "meet" Austin on the phone. He's supposed to be the "answer man" there BTW.
1/2 MOA is 1/2 MOA at any distance. The linear distance subtended by that arc varies according to this proportion: 1 MOA = 1" per hundred yards. The actual value is 1.047 inches but such precision is not necessary.
1/2 MOA subtends 1 inch at 200 yards.
It was a joke, but thanks for answering anyway.;)
AR15barrels
08-02-07, 20:40
But what's the MOA value at 200 yards?
:eek:
You're kidding right?
ETA: never mind, I just read through the rest of the posts...
Alpha Sierra
08-02-07, 20:51
:eek:
You're kidding right?...
:D That's what I thought.
Alpha Sierra
08-02-07, 20:51
It was a joke, but thanks for answering anyway.;)
You got me. For a second there I thought I had wandered to TOS. :cool:
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