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Discussion in 'Long Range Hunting & Shooting' started by NONYA, Sep 2, 2008.
Anyone have any data on spindrift using a 168 gr out of the .308 at distances 500+ yards?gun)
I'm fairly sure it's negligible at any distance within the capability of a 308.
All other variables fairly significantly over ride spin drift.
So what you dont think that it exists in a .308 win?
Here is a thread where they talked about it to great lenghts. It also has a webpage to caculate it.
Hope this helps.
Spindrift Calculation?? - Sniper's Hide Forums
Yep, it exists in a 308 and all other projectiles out of a rifled bore.
I just don't think it matters "that much" or I'm just not advanced enough in my shooting.
If I could ever master the "wind" thing then I'd probably think about spin drift a bit more.
Another thought, right or wrong, if one "sights in" on a far distant target and regularly hits it under no wind conditions, wouldn't spin drift automatically factored, though unknowingly, in to the process.? Just a tho't.
Roy hit the nail on the head with his comment. Worry about the wind and your rest....
You guys are going to laugh at me for this but this is how I beat spin drift.
I first set my scope dead level to the rifle or as level as I can get it. I then take the load I will be using the most and dial it in perfectly at 300 yards. with the use of an external scope mounted bubble level. I then (this is the tricky part) find a day and location when and where there is NO wind whatso ever. I ussually reserve this for the coldest of days and early in the morning when there is typically no air movment where I like to shoot. Then I set up at the maximum distance I like to shoot. For me it is 1000 yards. I then (paying extra special attention top that bubble level) begin to shoot at the 1K line. Most of my loads from my 308 have been 8-10" to the right of center. Then I loosen the left side of my scope ring screw a tad and tighten the right side a bit. With a bit of patience you can ussually get the scope a rotate a tiny ity bitty bit off of true plumb. By leaving the bubble level alone and shooting by that the rifle is essentially canted every time you pull the trigger. Whether you use hold overs of dial the knob it brings it back in line. Complicated? Yes. Peace of mind? You betcha!
Nonya , I'm very new to long distance shooting , so please don't take this the wrong way . this is just something I fought with and thought it could be a problem your having .
as my shots got longer my P. O .I . would go to the right . the longer the shot the more right I hit . I was messing with it one day at the range and a guy asked what I was doing . I told him and spin drift was his answer to my problem . but to make a long story short . my scope was not straight . as I went to a longer distance , I used a different ballistic mark . when I did that I got added windage from the reticle being tilted . and this should be true if you dial your elevation too .
again I'm very new to this and I went through this not long ago . I thought it could be something you overlooked ,if not sorry for butting in . Jim
Well I'll be darn'd. Its whatcha don't know that get ya and I didn't know. I just figured it took care of itself during the sight in and drop chart development.
However, I do rotate the scope after I've plumbed it with strings levels and such if its necessary when elevation is raised. I'll be shooting to 1k shortly and will watch for what you described.
Thanx for the links and the usefull data.I downloaded the program and the data I got from it almost matched my results EXACTLY. I was shooting in 0 wind down a canyon last sat and from 700 out I was noticing a right side drift,shooting bug holes at 100 and then moving right past 700.Seems spindrift does exist and there have been extensive tests to prove it,it varies from round to round but is always a factor.gun)
I am fortunate to have shot quite a bit at 1k over the past several months and can say that it does exist on every gun we have shot at that distance. EVERY shot has been to the right unless left MOA has been dialed in to correct it. This is in a gravel pit with high banks on boths sides making the wind have little or no effect. We have shot at all times of day with all different wind situations and the result is always the same - right of POA. All scopes have been painstakingly leveled with the action with levels, plum lines, feeler guages, etc. My conclusion is, and I am no expert, is either you sight it in left of POA to begin with (between 1 - 2 MOA), or you remember to dial it in at distance. I would also say not only does it vary round to round, but also from what we have seen rifle to rifle.