scope cant compensation

[wildchild]

Has anyone figured out the correct about of cant to put in the scope with a rifle setting level to compensate for spin drift of the bullet for longrange shooting. Noticed my bullets print to the right about 1.5" in a no wind condition so without cranking the windage to make up for it is there a certain degree of cant one and cheat into the scope mounting????
Topic maybe shoulda been bullet spin compensation ???

 

[whiskey08]

my engineer brother in law and I tried to work it out once.

First problem was the curve and your cant never really match up

2d problem was that your eyes will always try to center or straighten any cant.

after working on it for awhile we came to the conclusion it didnt make sense.

 

[wildchild]

my engineer brother in law and I tried to work it out once.

First problem was the curve and your cant never really match up

2d problem was that your eyes will always try to center or straighten any cant.

after working on it for awhile we came to the conclusion it didnt make sense.

LOL

 

[spclark]

Brian Litz covers that pretty thoroughly in his book on ballistics.

According to him the range is irrelevant, the time-of-flight being the important factor.

On p. 528 he states:

Drift = 1.25(Sg+1.2)tof1.83

Where:

Drift is in inches, in the direction of the rifling twist;
Sg is the gyroscopic stability factor according to Miller twist rule;
tof is the time-of-flight.

So work it out... but you may be better off just calculating the clicks needed as canting a scope induces a whole 'nother order of issues.

 

[artbosco]

Has anyone figured out the correct about of cant to put in the scope with a rifle setting level to compensate for spin drift of the bullet for longrange shooting?

See if this post by Dan Newberry, The effect of a canted scope verses a canted rifle... answers your question: http://practicalrifler.6.forumer.com/viewtopic.php?t=73

 

[Dennis Keefer]

Thank-You Outdoorsman for that link. That is an excelent post, and should be read by all.

To Dan Newberry, whom ever you are, excelent post.

 

[whiskey08]

Im slower than most so I dont understand the article and how it relates to spin drift.

the idea behind a canted scope is when you dial from 100yds to 700yds the crosshairs will follow a slant/cant that follows spin drift. For my .308 its about (per JBM caculator)
4.5" at 700 yds
6.3" at 800 yds
8.5" at 900 yds

problem with actually making it work is the amount of drift changes at each yardage, Even if you decide to intersect at a given range, because of the curve its hard to find a happy medium.