Can't understand cant

Mojo · Post by **Mojo** » Sat Sep 29, 2007 10:06 am

Can somebody please explain how canting a firearm effects accuracy? I just don't get it. Why does it matter if the rifle is rotated a few degrees in one direction or the other along the longitudinal axis of the firearm? How does that effect the path of the bullet?

Leverdude · Post by **Leverdude** » Sat Sep 29, 2007 10:19 am

Its easy if you think on it.
Since the sights or scope are OVER the barrel but angled slightly down, so the bullet rises as it leaves the muzzle the sighting system must be aligned in order to hit what your shooting at. Its only aligned when held level. The bullet rises & falls into your target. If you cant the gun left the bullet will be angled left & if you cant it right it'll go right.

Picture laying your rifle on its side & think about where the bullet will go.

If we were talking lazer beams it wouldn't matter but gravity effects bullets.

1894 · Post by **1894** » Sat Sep 29, 2007 10:23 am

My very unscientific opinion, Probably wrong but hope to be corrected if I am.

I think to understand cant , extend your arm , point at a spot with your index finger on top , make sure your wrist bone is in line as well . Then rotate your hand a few degrees each way. Add in the arc of trajectory and you have quite a change of POI

Phil

Tycer · Post by **Tycer** » Sat Sep 29, 2007 10:24 am

The sights are not inside the bore - they rest on top, on a different axis. If gravity did not exist, it would probably not matter, but since it does, your gun's elevation is sighted to take that into consideration. Cant it in one direction and the POI will change.

If you cant your gun the same all the time and have your gun sighted for you, at only one distance, it does not matter.

Because while canted, if you wanted to change elevation at the sights, it would take an adjustment of both elevation and windage screws to adjust only elevation.

don Tomás · Post by **don Tomás** » Sat Sep 29, 2007 1:39 pm

Post by **Chuck 100 yd** » Sat Sep 29, 2007 5:07 pm

there would be no problem if the rifle/pistol was canted at the same angle for every shot. It is the change in the amount of cant that causes your groups to open up.

Griff · Post by **Griff** » Sat Sep 29, 2007 5:21 pm

The only time canting a firearm worked with any degree of repeatibility and accuracy was when I was in-country during VN. I carried a Thompson 1928-A1 w/30 rnd stick mags. By holding it w/the mag base pointed to the left, muzzle jump (caused mainly by the bolt slamming rearward), was more efectively controlled.

cas · Post by **cas** » Sat Sep 29, 2007 6:12 pm

The farther away the target, the worse it gets.

ScottT · Post by **ScottT** » Sat Sep 29, 2007 6:38 pm

At close range, it makes little difference. However, it makes a huge difference at longer ranges.

bj94 · Post by **bj94** » Sat Sep 29, 2007 6:42 pm

Position of sights relative to bore doesn't matter that much, but trajectory does.

Consider a case where you have a high trajectory, maybe a black powder rifle shooting at long distance. The barrel is pointing up with respect to the line of sight. The bullet goes up, then comes back down and hits the target. If you cant the gun, then while the bullet is going up it is also going to one side or the other, then when it drops down to the level of the target it will be to the left or right of the point of aim.

When I shoot highpower rifle I have to cant my rifle depending on position. My club only shoots reduced targets at 100 yards, and I'm shooting 3000 fps or greater, so the change in point of impact due to canting is not a big factor. Some competitors determine the change in point of impact and adjust their sights for the different stages of the match.

CJM · Post by **CJM** » Sat Sep 29, 2007 6:57 pm

Mojo

Cant doesn't affect the trajectory of the bullet, but it does affect where the sights are pointing. When a rifle is canted, the sights are moved away from the impact point, so before you fire you "correct" your aim and cause the bullet to miss.

Mojo · Post by **Mojo** » Sat Sep 29, 2007 8:22 pm

Thanks guys, and double thanks for the effort with the graphics. I've read a lot about cant and its effect on accuracy but it's never been an issue with me as I've never been a long range shooter. I'm one of those people that can read about something 100 times but until I actually do it I really don't understand it. I'm obviously thinking about this way too much and analyzing it to death. I'm going to unplug, have a few frosty beverages and head-out to the range tomorrow morning for a little experimentation on the 200 yd. range.

Mojo · Post by **Mojo** » Sat Sep 29, 2007 9:53 pm

Aaaaaah. On the way home from the frosty beverage store I had one of those "OH S*&%" moments and now get it. I was right. I was thinking waaaaaay too much and didn't realize just how simple it was. I'm a 100 yds. or less hunter and have never really taken more than the occasional 200 yard+ shoot off the roof of my truck just for fun but I now understand how cant can be a problem for the long distance shooter. Thanks again!

Post by **Ysabel Kid** » Sat Sep 29, 2007 10:06 pm

Mojo -

Excellent post and topic!

Guys - the explanations were great. I learn something knew every day here. Helps with all the other stuff I forget every day!!!

Pete44ru · Post by **Pete44ru** » Sun Sep 30, 2007 10:07 am

[On the way home from the frosty beverage store I had one of those "OH S*&%" moments and now get it. ]

Yep - Epecially onct ya figger in, the gyrational instablitiy of the earth combined with the rotational torque of the can's pop-top !

Cimarron Red · Post by **Cimarron Red** » Mon Oct 01, 2007 1:53 pm

Although not pracitcal on a hunting rifle, this is the solution to the cant problem on a target gun:

http://i78.photobucket.com/albums/j88/c ... 010020.jpg

C. Cash · Post by **C. Cash** » Mon Oct 01, 2007 1:57 pm

don TomÃ¡s wrote:

Thank you for that hearty chuckle Don Tomas! Yes, great explainations and post....never really thought hard about why.

Old Ironsights · Post by **Old Ironsights** » Mon Oct 01, 2007 2:50 pm

Sadly, Birdman.org is no more. Some parrot-lover has co-opted the site.