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Cant...defined

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Irish Bird Dog View Drop Down
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    Posted: 30 May 2018 at 10:07
CANT is a physical thing related to shooting a rifle but you CAN'T shoot well if you do......so here is the explanation of why if you CANT you CAN'T maybe hit the "bullseye"....

Effects of Cant

by NRA Staff - Thursday, May 24, 2018

Effects of Cant

From the June 1955 issue of American Rifleman, a question and answer session reviewing the effects of cant.

While I have seen answers giving the effect of cant for certain cartridges at a given range, I would like to have an explanation which will be adequate for determining this effect with any cartridge at any range.George A. Williams, Brooklyn, NY.

Answer by E.H. Harrison: The effect of canting the rifle in firing is to move the impact of the bullet on the target in the direction of the cant, and also slightly downward.

Effects of Rifle Cant
The above illustration shows in perspective the effect of cant when firing at a vertical target with its center at the point T. The gun is at G, and the line GT is therefore the range. Because of the curvature of the trajectory resulting from gravity, the bullet must be discharged at an angle above the line to the target, and in the figure the point toward which the bullet must be discharged is P. If, for example, the rifle is canted to the right, the result is to discharge the bullet in the direction of the point P′. This obviously will result in the bullet striking to the right of the center of the target and also slightly lower. The latter effect is trifling and can be ignored, and the important result is to move the strike of the bullet from T to T′. We see that the magnitude of the effect is dependent on both the angle of elevation (which governs the height PT) and the angle through which the rifle is canted.

We can determine the total effect on the target from the magnitudes of the above two factors. PT obviously depends on the range and the angle of elevation. The sportsman seldom knows the latter, but he can obtain PT from the approximate relation that it is four times the midrange trajectory height. Trajectory heights for various factory loads at ranges up to 300 yards are given in factory ballistic tables. For example, the midrange height of the factory .270 Winchester 150-grain load when shooting at 300 yards is 7.8 inches, hence the height PT under those conditions is about 31 inches.

For the effect of the angle of cant C, note that the distance TT′ (which is the displacement on the target we are looking for) is given by the relation TT′ = PT sine C. The values of the sines of angles 1 to 6 are:

Effects of Cant | Sine
If in this case we cant the rifle 5 to the right, the displacement of the hilt will be 31 times .087 or about 2 inches to the right.

In the above way the effect of cant can be readily computed for any cartridge of known ballistics. We see that at long ranges or with cartridges giving quite curved trajectories, the lateral displacement on the target can be considerable. This is notably the case with the .22 long rifle.




Edited by Irish Bird Dog - 30 May 2018 at 10:08
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Post Options Post Options   Thanks (0) Thanks(0)   Quote BEAR Quote  Post ReplyReply Direct Link To This Post Posted: 30 May 2018 at 10:44
Just thoughts.

Most people shoot with scopes today, and often cant the rifle; some will say "your crosshairs are tilted".  But those same people hold the rifle crosshair on target as level.  this isn't canting.  Such rifles are sighted in on an angle to start with.

For most rifles, canting up to 2 degrees and normal hunting ranges, will not be noticed.


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Post Options Post Options   Thanks (0) Thanks(0)   Quote jsgbearpaws1 Quote  Post ReplyReply Direct Link To This Post Posted: 30 May 2018 at 15:12
I cant reach back between my shoulder blades and scratch anymore......that must be why my shooting is off?

That little scope level can be handy when going long.
...oh yeah! thats gonna hurt!
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Irish Bird Dog Quote  Post ReplyReply Direct Link To This Post Posted: 30 May 2018 at 18:09
Have a factory mounted Level on the bbl of my BPCR rifle at the muzzle end near the Globe front sight. 
Don't know when or even IF the old boys back when had a level, no idea when the idea came to be used on rifles to help adj for cant. The only cant I ever used prior was back in my youth and it was a CANT Hook. 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote RobertMT Quote  Post ReplyReply Direct Link To This Post Posted: 30 May 2018 at 19:53
Cant wont matter, inside few hundred yds, for hunting, it does at longer range.

Plumb bob was often used, before level, consider many of the buffalo hunters, started out providing meat for surveyors and for rail road crews, as well as scouting.   
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