Rifle cant induced error to POI

[Near miss]

Hello!

I read a document from the Resources site about cant error, written by hide member Nik H.

Here is an online excel file that will calculate it. The sheet has own tabs for US and EU users.

Cant calculator.xlsx

1drv.ms

To edit it please either download it, copy to your cloud or click the "Edit in browser" button.

One thing to point out:
Scope height is not a very important factor. The error is mostly caused by cant and flight time.

I had a hunch of this effect being more evident with rimfire but it still surprised me quite a bit.

The paper made by Nik can be found here:

https://www.snipershide.com/shooting/resources/estimation-of-shot-error-due-to-rifle-cant.22/

 

[Just Chuck]

With respect to Rimfire, I've heard that it is equivalent to .308 at 4x the distance. So 100 yard Rimfire is equivalent to 400 yards with .308 . This goes for wind calls, dope, and I suppose cant also.

Thanks for posting. Check it out when get to my PC. iPad is not good with Excel.

 

[Gunfighter14e2]

One day will poking a 600yd target I canted the rifle full left on a Harris bipod, the group moved just shy of .5 moa left, Canted to full right, it moved right the same amount. Mechanical offset was 1.878

 

[Near miss]

With respect to Rimfire, I've heard that it is equivalent to .308 at 4x the distance. So 100 yard Rimfire is equivalent to 400 yards with .308 . This goes for wind calls, dope, and I suppose cant also.

Thanks for posting. Check it out when get to my PC. iPad is not good with Excel.

Yes, that ratio is true. But with flight time it is only roughly 2.5x difference.

Distance: 100m
.308 - 0.14 sec
.22LR - 0.34 sec
Ratio of 2.42

Distance: 400m
.308 - 0.65 sec
.22LR - 1.7 sec
Ratio of 2.61

I am sorry the file is not attached but hide prohibits attaching .xls files to posts.

 

[Just Chuck]

I am sorry the file is not attached but hide prohibits attaching .xls files to posts.

On my PC now and was able to open the Excel file and do some plug in's on it.

Good to know info, but I do everything I can to eliminate cant so the calculator is good for demonstration purposes, but probably won't be used that much in my shooting ( I hope).

I didn't know about the 2.5x time of flight - thanks.

 

[Near miss]

On my PC now and was able to open the Excel file and do some plug in's on it.

Good to know info, but I do everything I can to eliminate cant so the calculator is good for demonstration purposes, but probably won't be used that much in my shooting ( I hope).

I didn't know about the 2.5x time of flight - thanks.

That is what this is for. To give concrete data so one can realize just how much it is.
I actually thought that cant is not a aerious problem and prioritized hold comfort over cant issues.

Now I see that I must be much more careful with it. If you want to make less than 0.4moa at 100m, you have to keep rifle cant basically under 1 degree at minimum. It is not hard in good position.

But even a small 0.2 degree variance causes offset of approximately one bullet hole.

 

[Near miss]

I think I will start to use targets with horizontal reference lines like crosshair pictures in the aiming point.

Then even if I will be off with the cant marked on to the paper, I will still be able to repeat the same cant for other targets and thus:
1. Reduce background groups that are combined from many groups. I am guessing quite a big of an impact if my estimated cant at the moment swings 0.2° for each side.
2. Reduce single group size in overall.

 

[Just Chuck]

I think I will start to use targets with horizontal reference lines like crosshair pictures in the aiming point.

Then even if I will be off with the cant marked on to the paper, I will still be able to repeat the same cant for other targets and thus:
1. Reduce background groups that are combined from many groups. I am guessing quite a big of an impact if my estimated cant at the moment swings 0.2° for each side.
2. Reduce single group size in overall.

I'm a bit sloppy when putting up my targets, as far being level. My thought is that I need to be working the bubble level on the scope and to b sure I've got that correct and not counting on the target being level.

 

[Near miss]

I'm a bit sloppy when putting up my targets, as far being level. My thought is that I need to be working the bubble level on the scope and to b sure I've got that correct and not counting on the target being level.

I remember that I have made this error also couple of times.
The result is me continuously trying to fight between the horizontal line at the target paper and the bubble level.
It certainly has its difficulties.

 

[FromMyColdDeadHand]

Wasn't there a thread in the rifles or scope section about cant and bubble levels and the use of levels was not seen as beneficial- as in learn how to hold a rifle and your head and don't cant a rifle.

I have bubble levels on all my rifles, reticles plumbed vertical and the bubble level to the reticle. They are fairly plumb to the action, but that is more comfort/position in prone. My issue is that bubble levels are 'sticky' and the bubble sometimes won't freely move, especially when moving small increments.

Interesting that cant isn't something that many, if any, scopes show in the reticle.

 

[Near miss]

Wasn't there a thread in the rifles or scope section about cant and bubble levels and the use of levels was not seen as beneficial- as in learn how to hold a rifle and your head and don't cant a rifle.

I have bubble levels on all my rifles, reticles plumbed vertical and the bubble level to the reticle. They are fairly plumb to the action, but that is more comfort/position in prone. My issue is that bubble levels are 'sticky' and the bubble sometimes won't freely move, especially when moving small increments.

I basically agree with them. Just learn to hold the rifle in the same position. But I can't do it yet and my bubble is the only teacher.
Naturally the mind will try to level with various things in sight picture. The more magnification, the more easily mind is tricked. And I always shoot both eyes open.

My Spuhr mount has bubble built in so I guess I am sticking with the it.
It is in a good place for learning experience - it does not show to me all the time, I have to check it by tilting head slightly.

I think the bubble in the spuhr moves more freely than the Wheeler on another gun. But I see Wheeler as adequate for a reference point.