Incline Shooting (Cosmine) Riflemans Rule

[Craig Fosse 286]

hi guys,

 

I finally got to zero my s200 in yesterday with the mtc mamba and the HUMA reg, with it now running nice at 14 ft/lbs,

 

after a rusty start I started getting some really good groups within a 5p piece and worked out my aim points all the way from 15 yards to 50 yards,

 

I have never shot out to 50 yards before with sub 12 because there has always been a lot of factors that could allow your shot to miss, especially with hunting and I personally don't like taking the risk, many shooters too who are probably far better shots than me.

 

I recently looked into the "cosmine" rule when trying to work out my aim points for incline/ decline shooting. I used to in my naïve days take shots at trees and leaves, but especially with the FAC airgun now my fall of shot has to be more and more watched with a careful eye.

 

anyway I found a useful site which explained with a simple sum of how you can work out roughly your incline shooting for 40 degrees up to 60., vertical as I now know does not have a trajectory path meaning you should be shooting in a straight line all the time (I think)

 

http://www.backcountrymaven.com/journal/tag/the-improved-riflemans-method

 

this was the site which made for an interesting read,

 

basically if you multiply your yards by the degree number (pre worked out) you can find out the actual yards you would be shooting at.

 

for example 50 yards at a 60 degree incline would be 50 x .500 = 25 yards.

 

therefore what I got from this is that you would take your aim point on the flat for 25 yards and use this at your elevated 50 yard target and you should be bang on?

 

so with this I came up and have made a table which shows my aim points...which will hopefully go to being taped to the inside of my scope cover and a bigger one to sit with me at the base of the hide

 

Yards Elevated 40/60 *

15 – B/CR 12/8 (actual point of aim)

 

20- +.1 15/10

 

25-Zero 19/12

 

30-zero 22/15

 

35- -.1 26/18

 

40 – h/c 30/20

 

45 B/C 35/23

 

50 Gap 38/25

 

the B/c are bottom of cross and H/C half cross as I am shooting on an SCB 2 reticle.

 

I am yet to put this into practice at incline shooting but I am hoping to soon, the one thing that I am wanting clarification on is,

 

when I am shooting at 15 yards on flat my aim point is shooting low.... as the trajectory of the pellet is still rising.

 

now if I take my table here

 

an inclined shot of 20 yards at 40 * would be technically shooting at 15 yards(rounded off),...would this mean due to my current rifles zero at an elevated position of 20 yards I will be on my low 15 yard aim point?...

 

I believe I do aim low, however books and theory in my head still thinks I should be aiming high.

 

another question is, if there is a target directly above you is it true that there is no trajectory and you should just aim at the birds arse or should you aim low again?....

 

as you can probably the tell the wind and weather here is horrendous so im doing some investigating before a day out roost shooting on the pigeons.....

 

Could you please refrain from asking me to check out chairgun, I don't really get on with it that well and have limited access

 

thanks

 

craig

Edited March 1, 2015 by Craig Fosse

[villaman 9,979]

Good read , but I think you need to get out more

[Craig Fosse 286]

So a vertical pigeon up in the tree I would need to aim low as if it was an incline then?

 

Haha can you tell its windy out here??,

 

I just wanted to know if I was shooting at an incline with what it says here I do infact have to shoot at my 15 yard low point of aim., guess the only way I will true y know is by testing and I can't get out because the weather is crap!

 

By the way in this by low I mean I have to apply hold over as the pellets are hitting low..

Edited March 1, 2015 by Craig Fosse

[secretagentmole 1,701]

Cosmine or Cosine??

[Craig Fosse 286]

Cosmine

[Durham John 693]

Cosmine or Cosine??

Cosine,

 

http://www.bbc.co.uk/schools/gcsebitesize/maths/geometry/furthertrigonometryhirev2.shtml

 

unless my long ago ( lol) memory of school maths fails me.

[Craig Fosse 286]

Perhaps it is I'm just going off the page I was looking at

 

Any answers to the questions?

[secretagentmole 1,701]

Perhaps it is I'm just going off the page I was looking at

 

Any answers to the questions?

 

 

Time for Specsavers Craig!

 

"The reason you need to be able to measure the line of sight angle is so you can calculate the cosine of this angle. Cosine is a fancy way of saying the ratio of the length of the adjacent side of the triangle to the length of the hypotenuse."

Edited March 2, 2015 by secretagentmole

[mark williams 7,549]

Double Dutch to me Craig.

Personally i would go back to this troublesome area of incline and put down markers where you are seeing and getting shots at the rabbits.

Take notes of the shot required ie,- marker A 1 milldot h/over , 11/2 milldot left side for incline. The rabbits nearest your markers gets chosen only.

Thinking about it shooting at an angle and also up or down hill the pellet will flying against gravity in two ways, not just one (i think).Permanent markers make sense to me.

Walking in the woods take a few shots at nurls or marks up in the tree canopy to teach yourself hold under or hold over.

 

Good luck & atb

Edited March 2, 2015 by mark williams

[Craig Fosse 286]

Haha maybe if I go to spec savers I might actually hit something

 

Cheers mark I remember you replying to the same question I asked a year or so ago! Looks like it's shooting at trees and trying,

 

But in sure if the COSINE rule is right my aim points will be what it is at that yards,

 

Be interesting to see for sure

[mark williams 7,549]

Might be getting older Craig but the old ways often work

 

atb