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Effects of rifle cant at 50 yards

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cj_86

cj_86

Member
Jul 3, 2015
311
41
Illinois, United States
Information: 
- Rifle is FX Bobcat .25 mk2
- Center line of bore to center line of scope measures aprox. 2.5"
- JSB Exact Kings .25 @ 25.4gr
- Range from rifle to target is 50 yards
- Little to no wind
- Angle of rifle cant was measured with a protractor that sat on elevation knob cap
- Angle of cant tested is 0 degrees, 10 degrees left & right, and 20 degrees left & right


Description:
I got another beautiful evening to do some more target shooting! Purpose of this test is to see what effect rifle cant has on POA/POI at a target 50 yards away. I chose 50 yards because majority of my hunting shots are taken from this distance. Each group consists of 5 shots, group #2 opened up because my brother-in-law decided to sit on my shooting table with me and eat his bag of Doritos, and the "oops" was because I forgot to cant the rifle at 20 degrees. The measurement is found by measuring the distance from the center of the "dot" to the centralize area of the groups.

Also, the reason I wanted to conduct this test is because I ordered a vortex bubble level because I'm a sucker for accessories! Anyways, while I wait for my scope level I decided to see for myself the usefulness of a level device. Anyways, enjoy!





 
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Thanks guys I'm glad you enjoyed the test! Everyone has been very helpful on this forum so anyway for me to pay you guys back. 

So my Vortex bubble level came in and I'm very pleased on the quality of the unit for only $36 on Amazon. It looks pretty beefy so I won't have any concerns of catching it on anything and snapping it off. I don't know why I torture myself by adding even more weight to already heavy gun ,but as I saw in my recent testing, the level device is a beneficial tool for those long shots.




 
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I just ordered a Weaver mounted level. Mounting directly to the Weaver rail or 11mm dovetail, you can use it to initially set up your scope reticle and also use it to avoid cant while shooting.

It seems to me the type that clamps on the scope tube rely on the scope reticle being perfectly level in the first place. That's why I prefer to mount the level on the dovetail or Weaver mount.

There's also the type that bolt to the scope rings using longer screws. That type is equal to the dovetail mount, but I think it may be harder to check with your non-shooting eye.
 
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Hey I am sitting on hold and reading as much as I can on this sweet forum. Just wanted to thank the OP for doing this. Wondered how much effect a cant would have if say on uneven ground with a bipod. We play a delicate game with gravity. If the rifle and scope relationship is no longer on good terms and gets twisted you will see the results as such. The target is in the sight picture but listing then the pellet falls out of a normal POI.
 
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I'm now wondering.... —

if you shot the same test, but with a pellet-weight / power combination that requires a lot of holdover (or elevation clicks) —

I'd think the effects would be much larger... 🤔

Would you mind testing that? 😊



And if we're shooting out to 100y, we'd have a lot more holdover yet — and a much bigger effect yet.... 😟



Matthias
 
Upvote 0
I'm now wondering.... —

if you shot the same test, but with a pellet-weight / power combination that requires a lot of holdover (or elevation clicks) —

I'd think the effects would be much larger... 🤔

Would you mind testing that? 😊



And if we're shooting out to 100y, we'd have a lot more holdover yet — and a much bigger effect yet.... 😟



Matthias
Click to expand...

No reason to test for this. It's physics/trigonometry.

Slower pellets take longer to reach the target. The longer the time of flight, the more drop. Cant error is a function of drop and cant_angle.

This is what you get with gun cant:

horizontal error = drop x sin(cant_angle)

vertical error = drop x (1-cos(cant_angle))


 
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Thanks, Scott, that's a cool formula!!

OK, here I'm trying it out, and it almost seems too small of a POI error. Am I doing this right?



Skyhawk .22 – zeroed for JSB Domed @ 50y
Shooting JSB Monster with 750fps – to 100y
Absolute drop (data from Strelok) @ 100y: 105cm
A likely cant error: 2 degrees

Calculation:
Horizontal POI Error
= Drop x sin(Cant Angle)
= 105cm x sin(2)
= 105cm x 0.035
= 3.7cm = 1.5"



Matthias
 
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