Well, well, well..... old dog learns new trick. I've never really paid much attention to spin drift. Over the years I have seen a few threads come up that asks about it and it seems the normal reply is that it "don't matter much"..... "too small a deviation to worry about", so I have always just kept the spin drift calculation turned off on my ballistics programs and ignored it. Why complicate things further if it is too little to matter??? I picked up a copy of APPLIED BALLISTICS FOR LONG RANGE SHOOTING (Bryan Litz) a few days ago. First, I was just browsing the book before settling in for a real in depth study and happened across the chapter on "gyroscopic drift". Bryan makes a few statements about how it is "subtle" effect, "extremely difficult to measure", so with my false security so confirmed, I moved on in my scan. At the end of the chapter I see a chart of the drift of a 750 grain .50 cal Amax out of a BMG. I have a 510 AM and that is the bullet I shoot so looked at the chart and it showed at 2500 yards the spin drift is over 81". NO WAY!, I thought..... at 1000 yards the chart shows almost 7". Now I am curious. I go fire up 4 different ballistic programs I have that do spin drift (including the one that comes with Bryan's book) and find much to my surprise that my favorite loads for my .338s all have 6" to almost 8" of spin drift at 1000 yards!!! I have noticed for years that as I move out past 500 yards my groups tend to drift to the right.... the longer the range the further right. I typically have a little "left to right" wind on my range so I blamed that, and I got really obsessed about making sure my scope was level. Still, to ring my 1000 yard gong I kept having to dial .5 to .75 moa left windage correction in. Now I know, spin drift is NOT something to be ignored. Not at ranges further than 500 yards anyway. I feel like such a DUMMY for letting this get by me for so long!!