Where: <span style="font-style: italic">Drift</span> is spin-drift in inches in the direction of the rifling twist <span style="font-style: italic">Sg</span> is the gyroscopic stability factor as predicted by the Miller twist rule <span style="font-style: italic">ToF</span> is the bullet's Time of Flight
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Redmanss</div><div class="ubbcode-body">I've been looking but can't find Spin-D for sale anywhere. Is there a vendor for it or is it still undergoing FDA testing?</div></div>
Don't waste your money on Spin-D. Big Rip Off! It's really just yellow #5 mixed with Frank & VJJ's ball sweat. The good stuff is the new and improved formulation of Spin-Xtreme aka "wind grease".
At 600 yards, when shooting my 300 win mag, 190 grain Sierra MK at 2960 FPS, I always have to put in one click left for spin drift. It isn't much, but it is enough to get me from the 10 ring to the X ring. (about 1.5 inches)
Another thing I have to figure in, is that as the barrel heats up (around round 10-12 in a 22 round string:2 sighters, 20 for record) the rounds drift upward. Eventually I figured out that the insulation of the stock on the lower part of the barrel causes the barrel to expand more underneath than it does on top where it gets more air circulation. It works just like the Bi-metal strips used in thermostats.
The lower portion of the barrel retains more heat because of the way the stock keeps air from circulating around it. Therefore, the lower part of the barrel expands more and pushes the rounds upward a bit.
My TRG22 has so much air circulation around the barrel, that it isn't an issue. The McMillan built M40A1 style rifle in 300 win mag has much less air circulation underneath the barrel.
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: kraigWY</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">I've been looking but can't find Spin-D for sale anywhere.</div></div>
You find it at Lowes, in the same asle as the prop dust powder.</div></div> Next to the grid squares and PRC-E7's?
When you get to those distances where spin drift is a major concern there are so many other factors (temp, humidity, swirling/angled wind) to insert in the shot.....fact is, there might be a half a dozen people on this forum that could effectually use spin drift to make a "better" shot. Many might include it in their shot calculation, but the vast majority will still have to walk it in....