Effects of Canting Rifles and Bullet Impact Changes

[jr600yd]

Geezzzzzzeeeeee....... my heads spining. Just turn the knobs and be done with it!

 

[Bart B.]

Bart- Not to sound like a bigger idiot than I am but you are saying that canting will cause you to shoot low to what ever side you are canted to IF the elevation is correct?? Because your rifle can not use the maximum elevation potential unless it is straight up. More or less.... Right?

Yes, when canted, bullets will drop below a horizontal line centered on point of aim. Not very much

That's because the bore is pointed at a lesser angle to the horizontal when fired. The bore points at the line of fire arc shown earlier.

If the rifle is canted right 90 degrees, the bore points in the horizontal plane to see the right. Bullets will strike right from point of aim equal to drop at target range. And the same amount below line of sight and fire.

To calculate horizontal poi shift, sine of can't angle X bullet drop at target range. Example - sine of 3 deg X 35 MOA drop equals 1.83 MOA horizontal shift.

To calculate vertical poi drop, cosine of cant angle X bullet drop at target range, then subtract answer from bullet drop at target range. Example - cosine of 3 deg X 35 MOA drop equals 34.95 MOA, 35.00 minus 34.95 equals .05 MOA drop below horizontal. Not very much and about 5.5 degrees cant puts bullet at the edge of a 6 foot square 1000 yard target paper and about .14 MOA low.

 

[howabouttheiris]

Was talking about this a long while ago with someone that was trying to figure out this for 3 Gun stages with a set cant angle (for example shooting thru a fixed slot in a wall). I drew the cases for 0 degrees cant, 45 degrees cant and 90 degrees cant .... with windage = 0, for simplicity.

It may help some with the discussion.

With worst case, 90 degree cant, you will miss by your bullet drop low and by your bullet drop right.

 

[dc.fireman]

As a prone sling shooter, I know that IF you cant consistently, everything comes up X's.

 

[Lone Hunter]

Im not but where is the RED line?

Fredo is making it...LOL

 

[KenOath]

Maybe the guys that shoot ELR like 2000 yards+ can chime in, surely cant at those distances would be noticeable??

 

[howabouttheiris]

Maybe the guys that shoot ELR like 2000 yards+ can chime in, surely cant at those distances would be noticeable??

Cant error is related to bullet drop, so it gets worse (as measured in inches) at distance. The 1st few degrees have a small effect in terms of elevation, but a relatively large effect in terms of windage.


For example.

My .308 at ~3150fps. 1125 yd = 373" drop.

A 5 degree cant will impact 2.5" low and 30" right.
A 10 degree cant will impact 7" low and 65" right.

 

[KenOath]

Cant error is related to bullet drop, so it gets worse (as measured in inches) at distance. The 1st few degrees have a small effect in terms of elevation, but a relatively large effect in terms of windage.


For example.

My .308 at ~3150fps. 1125 yd = 373" drop.

A 5 degree cant will impact 2.5" low and 30" right.
A 10 degree cant will impact 7" low and 65" right.

Consiideral movement, I have a level on my guns for FClass and 500m Bench, once Rifle is set up in bags level it generally stays put..

 

[Rustytigwire]

This is from an airgun page but the graphic is a good cant demo.

http://www.arld1.com/impactpointvscantangle.html