Canting

Here is my estimation.

AR's sight height is 2.6" above bore. 100yr zero is a single crossing zero. Fudging up for trajectory's curvature, the bullet's departure angle above horizon is 3moa. Bullet drop at 150yd is 4.5".

Canting 90 degree, windage is off 1.5moa to the left, and there is no upward velocity to compensate for bullet drop. Left-low 4.5".

45 degree cant, all components are multiplied by cos(45)=sin(45)=0.707. Bullet drop is partly compensated. Left 3", low 1.5".

-TL

Sent from my SM-N960U using Tapatalk
 
Your math assumes no offset error. Even very expensive sights can have offset if improperly mounted and cheap ones are almost certainly going to have offset error.

It makes a significant difference. This Blog article adds to the discussion by providing a clear visual aid to exactly what offset error actually means so we are on the same page.

From:

Canted Optics Zeroing Tips – 45 Degree Red Dot Setup
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By Ying
Blog post found here:

https://www.badassoptic.com/how-to-zero-a-red-dot-when-its-canted/
 

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Almost anything is possible, but I think it unlikely that being shot in the head caused the fold down rear sight to flip up.
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You would be surprised. Once had a guy with his intestines coming out the top of his head after being hit with a .50cal trying to crawl away.

Another guy looked like he was buried form the neck down after being at ground zero from a 2000lb JDAM strike. He still had his Hadji hat on....
His tongue hanging out was the only indicator all was not well.
Very creepy sight when we turned the corner on the climb up to do BDA.

It was actually meant as a joke though hence the smiley face. I appreciate you taking it seriously.
 
Great! I was hoping someone would either try it or carefully work out the math.
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There are too many variables to work out the math. The distance the optic is zeroed at will play a very significant factor. A traditional military BZO designed to be poa/poi at 25yds/300yds (or for the 20" bbl M16 33yds/300yds) will make your projectile hit pretty far left (my guess would be 6"+) and a little low at 130 yards using a 45 degree cant, moreso with a 90 degree can't.

Meanwhile, sighting the rifle to be dead on at that distance, theoreticaly, should leave you about 2.5" left and a good bit lower (6" or so is a from the hip guess).

In the end, it's a question that can't be answered without holding that particular rifle.

EDIT: and now I read again the original question and it specifically asks about side mounted sights, my guess was referencing the top sights only.
 
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Once had a guy with his intestines coming out the top of his head after being hit with a .50cal trying to crawl away.
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OK that is wild, and one-ups anything I've ever seen... and there's always someone who has seen more but I have seen far more very graphic images than I care to have.
 
5whiskey said:
There are too many variables to work out the math. The distance the optic is zeroed at will play a very significant factor. A traditional military BZO designed to be poa/poi at 25yds/300yds (or for the 20" bbl M16 33yds/300yds) will make your projectile hit pretty far left (my guess would be 6"+) and a little low at 130 yards using a 45 degree cant, moreso with a 90 degree can't.



Meanwhile, sighting the rifle to be dead on at that distance, theoreticaly, should leave you about 2.5" left and a good bit lower (6" or so is a from the hip guess).



In the end, it's a question that can't be answered without holding that particular rifle.



EDIT: and now I read again the original question and it specifically asks about side mounted sights, my guess was referencing the top sights only.
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Good point. I have been assuming 100yd zero, which may not be true with iron sight. My A2 clone has been modified to match the USMC sight. It has 4 clicks (2moa) below 300yd zero to have 200yd zero. I need to adjust the bullet's departure angle from 3moa to 4moa.

90 degree cant. 6" left-low at 150yd.

45 degree cant. 4" left, 2" low.

-TL

Sent from my SM-N960U using Tapatalk
 
Finally had a chance to experiment with my A2 clone.

150yd, iron sight. Elevation 300yd minus 4 clicks for 200yd zero. Without cant, poi at 150yd is centered and about 1" high. Normal.

45 degree cant. poi is 1.8" left, 0.7" high. Pretty much what I have expected. Quite easy to mount the rifle and aim

90 degree cant was tricky, both mounting rifle and aiming. Poi is 1.5" left and 6" low. I reckon the 2.6" sight height now compensates windage shift of the poi.

I highly doubt anybody can shoot well with 90 degree cant. It is simply too awkward. 45 degree is not bad.

-TL

Sent from my SM-N960U using Tapatalk
 
Confusing results. At least to me.

In all cases, the point of aim used was putting what would be the center top of the front sight with the gun held normally right where the bullet was intended to impact, right?

The lack of upward angle to the barrel at 90 degrees of cant resulted in the bullet going 6" low. Which means that there is enough upward angle when the gun is held normally to compensate for what would otherwise result in the bullet going 6" low.

Yet the bullet went less than 2" off target horizontally when that upward angle became a sideways angle and the gun was shot with 90 degrees of cant.

And how did the bullet go high with 45 degrees of cant? The vector breakdown says that some of the upward angle of the barrel that was compensating for the effects of gravity with the gun held normally is now going to be expended generating windage error--that should have made the bullet go lower than expected, not higher.
 
It is a 2moa gun. I only fired 2 shots for each setting, and eyeballed the mean position of the poi, so there could be errors. It is especially so for the 90 degree cant.

With 0 cant, poi is 1" above poa, or (0,1) in coordinates.

90 degree cant. Expected poi (-6,-6). Actual poi (-1.5, -6), relative to POA. The surprise is in x direction. AR has pretty high sight height of 2.6". With 90 degree cant that 2.6" sight height brings the poi 2.6" to the right, which I didn't include in my calculations.

45 degree cant. Expected poi (-4,-2), actual (-1.8, 0.7), relative to POA. It is higher than expected but still lower than 0 cant. The sight height brings the poi 1.8" to the right. Considering the probable error, it is in the ballpark.

-TL

Sent from my SM-N960U using Tapatalk
 
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