Aimpoint CompM2 Level?

[atek3]

How do I make sure my aimpoint M2 is level? It's on a Larue LT-129 mount.

thanks,
atek3

 

[highorder]

if it's properly mounted, it should be level. Do you have reason to believe its not?


edit:

do you mean side to side, or front to back?

if you mean side to side, you can use a machinists square and level the turret caps to the flat top of your rifle.

 

[Zak Smith]

Just eyeball it. It doesn't even have to be level. You can mount it at 45* with the knob on top if you want to, it'll just be more complicated to zero.

 

[Omnivore]

Yup-- eyeball it. Where the issue becomes critical is when you want long range accuracy, and even then what really counts is how you hold the rifle. That's where the mounted bubble levels, or anti-cant devices (ACDs) come in.

Now, If you're really, really concerned about being able to make frequent elevation changes without those changes affecting your windage... Naw, forget it-- you don't use a reflex sight that way, do you? Well, maybe you do. There's certainly no law against it. EOTech has those BDC reticles, but there you have no option of leveling the optic without a milling machine, so you would have to level your hold if you want to win that 1,000 yard match using a holosight.

 

[Omnivore]

OK; mount the adjustment knobs at 45 degrees to vertical, then always hold the rifle at 45 degrees, so the turrets are level and square. That'll work too.

Alright, I'm getting punchy and rude. Sorry (but it would work great).

 

[Zak Smith]

Where the issue becomes critical is when you want long range accuracy

Nope. Since the reticle is symmetric (has no orientation) and nobody dials elevation with knobs on an Aimpoint, it makes absolutely no difference.

mount the adjustment knobs at 45 degrees to vertical, then always hold the rifle at 45 degrees, so the turrets are level and square. That'll work too.

Nope. As long as you look through the rear of the Aimpoint, the orientation does not matter at all. You could mount it upside down. Sighting it in the first time may be more complicated, like I said originally, but other than that the Aimpoint has no concept of "up/down" or "left/right".

-z

 

[Omnivore]

Since the reticle is symmetric (has no orientation) and nobody dials elevation with knobs on an Aimpoint, it makes absolutely no difference.

Never say "nobody". There is no reason why you could not use a reflex sight just like iron sights, resetting to different elevation. You are correct insofar as most people never do it, and you are correct about the orentation of the sight within that limited sense.

EOTech might beg to differ regarding elevation adjustment changes, since they have BDC reticles for their holosights, exactly analogous to range setting on your AR-15 A2 sights. With only one dot, you could easily have multiple elevation settings, just like with a conventional scope or iron sights.

The shape of the reticle is irrelevant to the issue. This is a common misconception. What matters is that when you make adjustment changes, the axis of the motion of the reticle is exactly vertical with gravity (for elevation changes) and exactly level for windage changes (yes, for convenience sake, yes yes).

You could have a crosshair that is at 45 degrees, like an "X" and shoot just as well as if it were level and vertical, like a "t".

Nope. As long as you look through the rear of the Aimpoint, the orientation does not matter at all. You could mount it upside down. Sighting it in the first time may be more complicated, like I said originally, but other than that the Aimpoint has no concept of "up/down" or "left/right".

You are corrent to a point, but I am refering to the fact that, when you zero your rifle, you're holding it in a certain orientation (with the optic vertical over the center of the barrel in the most common of cases) and that as long as you repeatedly hold the rifle that way, your zero will work. If you then reorient the rifle, your "elevation" becomes partly windage, and your bullet will hit low and one side. Therefore, if you hold the rifle at a 45 degree cant, and you zero it that way, and then always shoot it with that same exact cant, you will shoot just as effectively as ever.

What you are doing, in effect, with elevation zero is actually tilting the barrel upward to compensate for bullet drop. Take a rifle with a normal zero, then cant it 90 degrees, and you now have no elevation angle at all-- your elevation has been converted into pure windage. Cant 90 degrees to the left, and your shots will hit way low and to the left. The reticle could be any shape, and all this still works exactly the same. We think of "leveling" a reticle with the rifle, bit that is assuming the motion vector of the reticle adjustments is exactly square with the reticle as it was installed at the factory. That usually works OK, but it is still based on assumption.

I stand behind every word. Just stop and think about it and I'm sure you'll agree-- we're talking about several different issues here, but I suspect we agree.

This setup below is a perfectly useable one. It's in effect a rifle that's been "canted" 90 degrees, but it could just as well be 45 degrees, or any other angle around the clock:
http://www.ultimak.com/pic36.htm

 

[Zak Smith]

Never say "nobody". There is no reason why you could not use a reflex sight just like iron sights, resetting to different elevation.

Find me one tactical shooter or competitor who has EVER adjusted the elevation of an Aimpoint sight "on the fly" to compensate for target distance in the middle of shooting for time and/or in a fight. Summary, nobody does it, it's not a repeatable operation under stress.

EOTech might beg to differ regarding elevation adjustment changes,

Since this thread was started specifically about the Aimpoint M2 and that was that my reply was about, my comments are about the Aimpoint specifically, not the EOTech. Furthermore, the EOTech does not have the mounting issue because it isn't mounted in a ring.

The shape of the reticle is irrelevant to the issue.

Uhh, no. If you had a TA11/31 reticle which contains vertical BDC elements, it sure as hell matters that it is square.

I am well aware of the changes in point of impact vs. line of aim when shooting a rifle that has been rotated vs. the orientation when it was sighted in. That has nothing to do with the originally query about getting the Aimpoint square in the mount -- not rotating the entire rifle, which is the tangent you've taken.

Rotational orientation of the Aimpoint makes no difference in long-range accuracy - as you claim - nor does one have to "hold the rifle at a 45* angle" if the Aimpoint is mounted with the knob at the 12 o'clock position, as you claim. The only affect is that zeroing the dot is more complicated like I said in the first reply.