Re: Long Range shots - elevation right on always to the right
You should expect to experience 6-8 inches of rightward drift at 1000 yards from a right twist barrel due to "Spin Drift". It's caused by the high speed rotation imparted to the bullet by the bore's rifling. If you live in the Northern Hemisphere, depending your direction of fire (azimuth of fire), you could expect to experience an additional 2 inches of additional rightward drift due to the rotation of the earth - a result of the Coriolis effect, often referred to as Coriolis Drift.
These sources of drift should be experienced even if all of your equipment is set up exactly plumb with the world. Even if you've done everything exactly perfect & correct. Believe me. I've been there, done that. You will run into those that say it isn't so. Be cordial, and then dismiss everything else those individuals have to say concerning this matter.
They're disregarding facts of life as they exist on this planet, as proven by the best and brightest minds. NASA and the US military incorporate corrections for this as a standard operating procedure. So unless you believe they're full of __it, you'd best believe, study, learn, and adjust.
You'll find others that ask; is it significant to be worth correcting for when a 1 mph cross wind-caused drift at 1000 yards can be the equal in magnitude. You'll have to answer that for yourself. Spin drift occurs with a specific bullet out of the same rifle to the same exact magnitude with each and every shot. Would you ignore the comparative drift if the source was a 'known' 1 mph cross wind. If you would, then you'd have to be happy with an aiming error of ~6-8 inches at 1000 yards.
Now I agree it's also important to have the rifle scope tube mounted parallel with the rifled action, and the cross hairs in the scope aligned vertically with Earth's gravitational pull. But understand with all else being correctly accounted for, you WILL experience a rightward drift from a right twist rifled barrel of approximately 6-8 inches over a distance of 1000 yards due to the bullet's rotational spin on each and every shot fired. And Coriolis Drift in the northern hemisphere could add another ~2 inches of rightward drift.
So the majority of the drift you're experiencing is to be expected. There may be some additional rightward drift being added due to equipment setup. You should be feeling good about life. Much better than if you weren't observing any rightward drift. It's a fact of life. There are ways to account for it. If you're only shooting at game with kill areas substantially larger than the magnitudes of these sources of drift, then you can zero about 1 inch left at 100 yds, and split the difference in the left-right error that will occur over the 1000 yards. If you're targeting itsy bitsy voles, then you'll pretty much have to add the dope for Spin and Coriolis drift on each and every shot.
I've spent days researching these topics, and finally came to peace with them.
Last edited by phorwath; 08-24-2011 at 03:20 PM.