Rifled barrels in firearms

Rifled barrels induce spin in projectiles, right? If someone were to dispute that, how could it be proven, short of high speed video?

Rifling marks on the bullets. They’re not straight and parallel to the direction of travel.

Make a mark on the top edge of a bullet, fire it at a target, and see where the mark ends up. Usually, it won’t be at the top of the bullet any more. I don’t know if bullets are consistent enough that you could find the angle as a function of range (which would give you the rate of rotation), but it would at least prove that they have some spin.

The first rifles were muskets that had been rifled, and a lot of them still fired round balls. A smooth bore musket pretty much always fires a curve ball, because the ball is going to randomly contact one side or another of the barrel as it goes down, giving it a spin. The ball will go straight for about 50 to 75 yards, and after that, where it goes is anyone’s guess. They used to say that you could stand 200 yards from a single musketeer and not fear being shot by him. A round ball fired from a rifled musket will go straight for a couple hundred yards.

If anyone doubts that rifling spins the bullet, ask them to explain why rifling a musket makes it so much more accurate.

(I happen to own both a smooth bore musket and a rifled musket, and can absolutely confirm from personal experience the accuracy difference between the two of them)

Another method: If you shoot a bullet into an iced over lake, sometimes you can end up with the bullet spinning. There are some videos on youtube showing this. Mythbusters found that while this was confirmed, it’s not easy to reproduce.

MythBusters S09E07 Spinning Bullet:
Youtube
Wikipedia

Would you attempting to assert

  • spinning them is of no value
    or
    [ii] rifling does not impart spin?

Make one half of the bullet (lengthwise) a different color* Take a single exposure in a dark room of the bullet using strobe light illumination. The bullet will be pictured at several points in its trajectory, apparently “stopped” in midair. You should see some images with a light and some with a dark side, or at least some images where it is transitioning from one to another, with different amounts of light and dark visible.
Of course, high speed video is incredibly easy to do these days (much easier than when I used it for my bachelor’s thesis), but you wanted something that didn’t use high-speed imagery. Strobe photography qualifies.

*It has to be some marking method that will survive firing out of the gun. I suspect paint won’t work, but jacketing two halves with different metal, or casting the shot from two different materials, or some such, might do it.

Of course, then you have to prove that the weight of the paint, or the weight differential of the material or jacketing is not what’s causing the spin.

well then you paint both sides with contrasting colours of paint.

Why? They just want to know if the bullet spins.

If you’re asking me (OP) then, no to both. I was just wondering how rifling induced spin is proven without using high speed video/ photography.

If someone doubted that rifling spins a bullet I’d be surprised if they could grasp the physics behind ballistics accuracy (related to bullet spin or otherwise). I mean, it’s Physics 101 (the concepts anyways), but if you doubt that rifling imparts a spin on the projectile then you’re probably not cut out for physics anyways.

Here’s what I’d say, if anyone doubts that rifling spins the bullet, ask them to prove it. They made the assertion, ask them to back it up.

Just show them this video.

I was going to come in and post what Crafter_Man posted. You don’t even have to paint them to see them rotating.

It seems to me that rather than trying to confirm using the actual bullet, it might be more useful to use a football or basketball. See what the accuracy difference is by simply throwing one of those puppies with and without spin.

Crafter_Man, how do you show them that video without using high-speed video?

And then there is “straight line rifling” which Hogg <sic?> and others claim as the origin of rifling. It wasn’t so much for accuracy (although it did help) as it was to provide a sort of “fouling groove” to make loading easier. I had a circa 1850 double that was straight line rifled as a sort of elephant gun.

If you’re taking what amounts to a set of still pictures, you don’t see rotation at all. You have to have something to indicate that rotation has taken place between exposures. If you’re saying that markings on the bullet will be visible, I agree. But it wasn’t clear that they would be, which is why I suggested the undeniable expedient of gross markings.