[dcriner]

A spinning bullet deflects significantly, left or right, due to gyroscopic action. This, of course, is well known and becomes more significant at longer ranges. My .30-'06, 1903 Springfield has a sliding rear sight, that automatically moves, left and right, depending on range, to compensate.

Now, let's back up in time - to my .58 cal., U.S. 1863 Springfield rifle musket - firing Minie balls and black powder. It has three flip-up leaf sights - for 100, 300, and 500 yards. But, the three sights are aligned the same, left to right - no compensation for gyroscopic drift. Was gyroscopic drift unknown then? Or maybe the slower muzzle velocity rendered the drift insignificant?

 

[WHSmithIV]

There probably isn't any significant rifling in the musket so the minie ball doesn't actually get anything significant in the way of gyroscopic spin. Also, back in the 1860's it's quite likely that gyroscopic spin wasn't much understood yet.

 

[dcriner]

The bore is fine on my 1863 Springfield. But, you are correct, the rifling grooves are rather shallow by modern standards.

 

[Diamondback]

Since the 03 has a right hand twist on the rifling, why would you need to adjust for gyroscopic drift to the right at any range? Usually the need for side to side adjustments is for the wind drift at longer ranges.

 

[Alpo]

Really makes you feel dumb, when you get as old as I am, and been playing with things that go bang as long as I have, and something is "well known", but I've never heard of it.

 

[Albtraum]

I think this only comes into effect at extreme ranges, 1000+ yards to over a mile. The windage settings on the rear sight aren't for the gyroscopic drift, but, for wind. Or if your open sights happen to shoot to the left or right.

 

[bntyhntr6975]

You mean its not to help compensate for the Coriolis drift?? Itd only make sense, it moves left or right, for the compensation needed, depending on which hemisphere you're in and the direction of your twist. Or maybe for Magnus effect? Na, lets stick with needing to factor in the Coriolis, since its open sights afterall.

 

[bntyhntr6975]

Seriously though, the 1903 DOES have built in compensation for spin drift. Supposedly, this can equate to 13" at 1000 yds. The rear sight actually moves to the left a little as it raises. This is just what i have read, i dont have one handy to verify. As for the musket, its big, heavy, slow, and barely spinning. And in that time, most likely not even thought about yet.

 

[Hawg]

Seriously though, the 1903 DOES have built in compensation for spin drift. Supposedly, this can equate to 13" at 1000 yds. The rear sight actually moves to the left a little as it raises.

So does the Buffington sight on trapdoor Springfields. The 1863 .58 Springfield was only good for 800 yards on man sized targets so there was no real point to it.

 

[carver]

Like Alpo, I have never heard of this, so I looked it up. If you are shooting at very long ranges, it does have some effect. Wikipedia says 1" at 2,000 meters. https://en.wikipedia.org/wiki/External_ballistics

 

[rcairflr]

Like Alpo, I have never heard of this, so I looked it up. If you are shooting at very long ranges, it does have some effect. Wikipedia says 1" at 2,000 meters. https://en.wikipedia.org/wiki/External_ballistics

.
Thats why my groups aren't as well as I like at 2000 meters.

Now I know what to blame

 

[Grizz]

Like Alpo, I have never heard of this, so I looked it up. If you are shooting at very long ranges, it does have some effect. Wikipedia says 1" at 2,000 meters. https://en.wikipedia.org/wiki/External_ballistics

That's kind of weird, for my 338 lapua I have to dial 1.8 moa for spin drift correction at 2000 yards. That comes out to 38" of correction that need to be accounted for if you plan to hit your target.

 

[JLA]

A spinning bullet deflects significantly, left or right, due to gyroscopic action. This, of course, is well known and becomes more significant at longer ranges. My .30-'06, 1903 Springfield has a sliding rear sight, that automatically moves, left and right, depending on range, to compensate.

Now, let's back up in time - to my .58 cal., U.S. 1863 Springfield rifle musket - firing Minie balls and black powder. It has three flip-up leaf sights - for 100, 300, and 500 yards. But, the three sights are aligned the same, left to right - no compensation for gyroscopic drift. Was gyroscopic drift unknown then? Or maybe the slower muzzle velocity rendered the drift insignificant?

Youre talking about spin drift and it tends to slide in the direction of the rifling pitch. And the faster the pitch the more it drifts. In the days of the rifle musket the concept of rifling in a barrel was still new. the reason they didn't figure out about spin drift then is because of the low velocity and slow twist rates. In the late 1890s when smokeless powders first came about they found that this newfangled propellant made far greater velocity, so work began to maximize it by redesigning projectiles. Longer sleeker projectiles sure fly straighter but they also need much more rotational force to remain stable in flight, so consequently rifling twist rates increased. Then they noticed their sight alignments didn't mesh up at distance anymore, and the true science behind external ballistics was born. Spin drift can be calculated today and figured in with a good windage call. Military sights, as on your springfield rifle are generically compensated for spin drift using the very load that rifle was intended for. Which would have either Been M1 ball or M2 ball depending on date of manufacture/rearsenal.

today it is a big topic of discussion among long range shooters and military snipers.

 

[JLA]

You mean its not to help compensate for the Coriolis drift?? Itd only make sense, it moves left or right, for the compensation needed, depending on which hemisphere you're in and the direction of your twist. Or maybe for Magnus effect? Na, lets stick with needing to factor in the Coriolis, since its open sights afterall.

The coriolis effect has more to do with the rotational speed of the earth and the curvature of its surface. As you can imagine it only has a significant effect at extreme range.

 

[RJay]

Of all the things in the world to worry about, this issue is not one of them