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Posted: 1/7/2005 8:49:35 PM EDT
Ok, I know I will get a few , but I thought that this was interesting.

I was messing with my ARMS #40A2 BUIS and placing it weird parts of the gun and rails. I tried placing the site all the way up to the rail slot from the front of the receiver. I tried looking through it expecting something stupid and useless, but for some reason it seemed interesing; my eyes were able to focus on the front sight much easier that when the BUIS is in its correct position. I know if you were to try to shoot with it like that your accuracy would be hurt because of the loss in the front to back sight distance or (sight radius?). I also remembered the purpose of the new La Rue Cantilever mount that brings the AIMPOINT or TRIPOWER to the hump between the receiver and the handguard.

Would this awkward position be beneficial in any way?
How much would it decrease accuracy?

I will note that the movement of the BUIS forward does looks quite strange.

If you could try this if you have a BUIS that would be appreciated; I would like a few opinions and some good laughs for my silly idea.

Thanks again for looking,

M11293
Link Posted: 1/7/2005 8:52:32 PM EDT
Link Posted: 1/7/2005 8:54:53 PM EDT
You mean like this:



I used to do that when I was using the Trijicon mount with my Compact ACOG. It was the only way I could get the scope far enough back and still have a BUIS. I got the idea from my rifle instructor - he does the same thing for his ELCAN with a GG&G MAD.a

BTW it works fine, not as precise as the full length sight radius, but I have no problems using it to 100y (furthest I tried). However I am glad LaRue made a better mount so now I have this:

Link Posted: 1/7/2005 8:56:01 PM EDT
I would think that the closer the BUIS is to the Front sight, the less accurate the overall round placement would be.

Conversly, the farther way, the more accurate.

Imagine placing the BUIS 3 inches away from the front sight, I'm sure that accuracy would suffer greatly.

Any engineers out there?
Link Posted: 1/7/2005 8:58:08 PM EDT
We all did it dude, but I couldn't tell where the round would go or if you could zero it that way but it screws up the sight radius inherent in the M16 sights. I think it would probably make the poi closer than your intended zero would be.
Link Posted: 1/7/2005 8:59:06 PM EDT

Originally Posted By xanadu:
I would think that the closer the BUIS is to the Front sight, the less accurate the overall round placement would be.

Conversly, the farther way, the more accurate.

Imagine placing the BUIS 3 inches away from the front sight, I'm sure that accuracy would suffer greatly.

Any engineers out there?



No, I am not an engineer, but I do know that the shorter the site radius the less accurate you are going to be; it is due to some sort of depth perception with the human eye.

Best example would be a S&W 4" is just as accurate as a 6"; only the extra 2 inches of site radius provide better depth perception to the human eye therefore, creating better accuracy.
Link Posted: 1/7/2005 9:02:59 PM EDT
I just switched mine to see.

Seems like it would be easier to center the sight post.

Maybe that is why the 20'' sight radius is better also.

With a CAR length it seems like you have tons of space around the post.

I may have to try it like this next time I go shoot.
Link Posted: 1/7/2005 9:06:47 PM EDT

Originally Posted By SickMAK90:
I just switched mine to see.

Seems like it would be easier to center the sight post.

Maybe that is why the 20'' sight radius is better also.

With a CAR length it seems like you have tons of space around the post.

I may have to try it like this next time I go shoot.



I am going to try it out; just for curiousity.

I guess I am not all that original after all.
Link Posted: 1/7/2005 9:09:42 PM EDT
I suck with the irons so far....so I'm sure this won't make it any worse.

I seriously suck...I shoot sub-moa with a crappy scope but give me a peep and I can't hit the broad side of a barn. I need more practice.
Link Posted: 1/7/2005 9:17:17 PM EDT

Originally Posted By SickMAK90:
I suck with the irons so far....so I'm sure this won't make it any worse.

I seriously suck...I shoot sub-moa with a crappy scope but give me a peep and I can't hit the broad side of a barn. I need more practice.



In the same boat.
Link Posted: 1/7/2005 9:26:31 PM EDT

Originally Posted By xanadu:

Any engineers out there?



Right here.

Accuraccy isn't effected - as that is all due to the barrel and ammo. It's the precision that is tougher to acheive with the shorter sight radius.

In other words no matter where you place the sight your rifle is just as inherently accurate as it's always been - the shorter sight radius however makes it difficult for you to precisely aim the weapon at the same place.

It MIGHT make QCB presentation quicker with the sight pushed out, I'd have to run drills with the timer to see. Having done it both ways though I can tell you I much prefer it closer and I'm more accurate that way (the KAC 600m sure helps as well )
Link Posted: 1/7/2005 9:35:22 PM EDT
The problem with moving it forward is it DOES screw up the geometry involved in the sight line and trajectory convergence.

For argument's sake let's consider the boreline instead of the trajectory and sightline. They make up two legs of a right triangle, with the third leg being the distance from the bore line to the aperture of the rear sight. If the bore line is level, then the sight line must angle downward to converge at the point of impact. (Yes, I know, we're ignoring ballistics, but the principle is the same.) The line from the bore to the aperture is vertical.

Draw you a right triangle representing this example. Make the base say, 12 inches long and the vertical 4 inches high. The top of the vertical will represent your sight aperture, and the point where the "sightline" and "boreline" meet is your Point of Impact. Halfway along the horizontal line draw another vertical line connecting to the sight line. This will represent your front sight.

Now move toward the convergence of the sightline and bore line about two inches and draw another vertical line 4 inches high. This is now your new rear sight position.

The top of the new vertical line is now above the sightline.

From this diagram, it is easy to see that if you move the rear sight forward, you are going to have to lower it to keep the same point of impact.

I quit. My head hurts now, and I last took geometry in the Johnson Administration.



Lonny
Link Posted: 1/7/2005 9:47:41 PM EDT
[Last Edit: 1/7/2005 9:54:56 PM EDT by JayCeeNC]
Already been done.

D&L Sports CQB Sight for more pictures.

Link Posted: 1/7/2005 9:55:13 PM EDT
[Last Edit: 1/7/2005 10:02:33 PM EDT by Onslaught]
The entire Canadian Army has been doing it this way for years

Link Posted: 1/7/2005 9:56:39 PM EDT

Originally Posted By Onslaught:
The entire Canadian Army has been doing it this way for years



IIRC they STORE them forward of the Elcan - but they move them to the rear when they need to use them.

Hopefully KevinB will jump in with the details.
Link Posted: 1/8/2005 6:17:08 AM EDT
I was thinking more for a close combat situation. I think it allows faster target accusition.
Link Posted: 1/8/2005 6:32:52 AM EDT


Right here.

Accuraccy isn't effected - as that is all due to the barrel and ammo. It's the precision that is tougher to acheive with the shorter sight radius.

In other words no matter where you place the sight your rifle is just as inherently accurate as it's always been - the shorter sight radius however makes it difficult for you to precisely aim the weapon at the same place.

It MIGHT make QCB presentation quicker with the sight pushed out, I'd have to run drills with the timer to see. Having done it both ways though I can tell you I much prefer it closer and I'm more accurate that way (the KAC 600m sure helps as well )

+1
Link Posted: 1/8/2005 7:09:17 AM EDT

Originally Posted By bigbore:
Some like it that way



Damn, I've heard of nose-to-charging handle, but that guy looks like that charging handle could be half way in his mouth.
Link Posted: 1/8/2005 7:52:23 AM EDT
I can't imagine how it would be quicker in a CQB application. Now you have to line up two pieces, both of which are far away from your eye.

It's much quicker to use the large aperture as far back as possible -- establish cheek weld and you are already lined up looking through the rear. At that point it's just a matter of getting the front site on target.
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