I don't notice it at 500, but at 800 and beyond spin drift is definitely something you to have to account for. What are your observations?

I think spin-drift is minor enough that, on shots closer than 500, it's irrelevant. However, my 600 yard range makes spin-drift clearly obvious.

I see all the shoot-n-see patch holes and they're predominantly right-of-center on the target even though that's not marked so by the prevailing winds.

I have a 901 yard range too (wish it was an even thousand) and it becomes a real factor.

It sounds like our observations are parallel.

Zeke

Spin drift is definitely a factor with a Sharps. I get about the same amount of drift with the 40 cal. Sharps and 380 to 400 grain bullets as I do with the 45 caliber with the 490 to 510 grain bullets. Something on the order of 4 inches at 300 meters and six or seven inches at 500 yards.

It is something you automatically take into account when you shoot one of these rifles. In fact, the original 1873 Trapdoor Springfield military rifle had the rear sight machined so that as you raise the elevation leaf, the sight notch moves to the left as well as up. The old timers were aware of this phenomenon and made a sight that was self compensating. These sights were correlated to 2000 yards.

I've noticed that the Swedish Mauser rear sights have a spin drift shift on the slider with the ladder up.

For me, after wind, cant is the next biggest error. Maybe in kansas it would be easier to eyeball what level is. I finally broke down and put bubble levels on my LR stuff and practice checking them with my other eye while setting up a shot. It seems like the scope makers could put a little level inside the scope that's visible in the reticle.

Spin drift is there, but I usually just add it in to my wind estimate for the cold bore shot. Then once I see where that lands it's all about the wind.

I think some people have experimented with intentionally installing their scope with a cant, such that you get a little bit of windage with a big elevation adjustment.

quote:

Originally posted by jpl:
For me, after wind, cant is the next biggest error. Maybe in kansas it would be easier to eyeball what level is. I finally broke down and put bubble levels on my LR stuff and practice checking them with my other eye while setting up a shot. It seems like the scope makers could put a little level inside the scope that's visible in the reticle.

Spin drift is there, but I usually just add it in to my wind estimate for the cold bore shot. Then once I see where that lands it's all about the wind.

I think some people have experimented with intentionally installing their scope with a cant, such that you get a little bit of windage with a big elevation adjustment.

I don't know how you can shoot LR without a level.

With my 510 whisper (subsonic Amaxs w/ 1:9.5" twist) it is equal to a 7.5mph wind. It is definitely noticeable even at 200yds.

At 1000mtr with no wind, my 300WM with 215gr Bergers at just over 3100fps at the muzzle, has just over 12” of drift to the right.
Even at 600mtr there is need to adjust for drift.
My 6.5x47 and 264WM have slightly more due to the 1:8” twist rate.

Cheers.

Spin drift or a bullet slowing down and yawing taking it off course.. who coined the word "spin drift".

quote:

Originally posted by Atkinson:
Spin drift or a bullet slowing down and yawing taking it off course.. who coined the word "spin drift".

These aren't the same thing at all. You're describing sub/trans-sonic instability vs calculable drift due to the high rate of spin.

quote:

Originally posted by Atkinson:who coined the word "spin drift".

Well, it's a term used to describe drift due to the spin on the bullet. What should it be called?

Here is a good explanation:

http://www.appliedballisticsll...copicAndCoriolis.pdf

Right hand twist barrels produce a right spin-drift (impact) whereas it's the opposite with left twist rifled barrels. Meaning; clockwise spin will print to the right at long range. Counter clockwise twist will produce an impact to the left.

This is totally different than instability yaw.

Zeke

quote:

Originally posted by ZekeShikar:
Right hand twist barrels produce a right spin-drift (impact) whereas it's the opposite with left twist rifled barrels. Meaning; clockwise spin will print to the right at long range. Counter clockwise twist will produce an impact to the left.

This is totally different than instability yaw.

Zeke

Brian Litz did a test using two identical rifles: one was a LH twist, the other a RH. He alternated shots at 1000 yds. There were two distinct groups; the distance between the centers divided by two was the actual spin drift. He did that experiment to verify his ballistics formulas, which I have to say are pretty accurate.

I shoot every week (not this week or next cuz I am in Australia) at 1190 yards - spin drift at that range is about 1 MOA with my Lapuas.

Thanks Tyler and AZ, that cleared things up..I was aware that twist would move a bullet at long range in opposite directions btw, so that helped..I was just curious of the "verbalolgy"