For what purpose do rifled barrels put a spin on a traveling bullet?

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Does it give it some sort of added benefit like traveling further vs no spin? Why does that happen physics wise?

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Smoothbore weapons were wildly inaccurate. Adding a spin on the bullet makes it more aerodynamic, so it doesn’t have to fight the air as it moves.

It creates accuracy.

A spinning bullet or football stays on the thrown path. Where a non spinning ball can wobble all over the place due to imperfections and wind

It stabilizes the bullet, keeping it pointy end first.

Arrows have fletches on the side to keep it going point first. A bullet normally doesn’t have that. The center of gravity will shift the heavy back end towards the front. This will disrupt the path of the bullet as well as affect the aerodynamics meaning the range and trajectory will also be negatively impacted.

Objects that spin are more stable. Look at a children’s toy like a top, or a gyroscope. Applying that to a bullet will improve its accuracy and keep it pointing in the direction it was fired, as opposed to spinning out through the air.

For a cool demonstration, check out the Slo Mo Guys firing [*tank shells*](https://www.youtube.com/watch?v=xpJ8EoGmLuE) where the tank’s barrel gives them that spin.

Spinning things are “[stabilized](https://en.wikipedia.org/wiki/Gyroscope)”, they’ll maintain their axis of rotation. You can see this with a [spinning top](https://a.c-dn.net/b/1XEUcn/spinning-top-candlestick_body_GettyImages-153605568.jpg.full.jpg) which balances itself on a very narrow point and keeps its balance for as long as it spins.

So the effect on bullets is that the bullet will not tumble end-over-end, it will basically travel in the same “orientation” all the way to the target. This lets the bullet “pierce” the air with its tip rather than its tail or side wall, so it travels much more accurately to the target.

It makes the bullet more accurate. The rifling causes the bullet to spin, which gives it a more stable flight path and makes it more accurate.

A really good example of this phenomenon is the fastball and knuckleball in baseball. A [fastball](https://www.youtube.com/watch?v=v5oDTxcex0k) is thrown with a significant amount of backspin. This causes it to have a stable and predictable flight path. As you can see in the linked video fastballs usually go pretty straight. There are fastballs (such as a cut fastball or two seam fastball) which intentionally break in one direction or another, and non-fastball pitches (changeup, curveball, slider, etc.) that do so as well, but the same principle applies: the spin creates a specific and predictable flightpath.

The [knuckleball](https://www.youtube.com/watch?v=EgmQV9sodUA) is intentionally thrown with essentially zero spin. This causes it to have a slower speed and a very unpredictable flightpath. You can see in the video that the knuckleball darts and floats around, it moves in an unpredictable way. However it is also much less accurate. You will also notice that, as compared to the fastball, the pitcher and catcher have much less of an idea where it will go. In the fastball video the catchers have essentially no problem catching the ball despite the fact that is traveling at speed in excess of 95 or 100 miles per hour. In the knuckleball video they frequently miss or drop the ball.

This is essentially what is happening with a bullet. Muskets, which were “smooth-bore” weapons with no rifling, were quite inaccurate. A late 18th century musket could hit a target as far as 300 meters away, but could only reliably hit a target from about 100 meters away. For comparison a mid 19th century rifle, like those used in the American civil war, could reliably hit a target from about 450 meters.

Stability. basically, bullets can tumble and having a twist creates a stable projectile.
A 55 grain bullet going through a barrel with a 1:6 twist (1 twist for 6 inches of barrel) is going to be spinning around faster and cause instability it might not tumble, but you might not be getting the accuracy or results you want when hitting a target.

Take That same 55 grain bullet and put it In a 1:9 twist barrel the bullet will be rotating slower and less likely to fly off target. Because of Slower rotation.

Bullets that rotate will fly farther, they use the rotational force given from the rifled barrel to stay slightly aloft, more “hang time” for lack of better term. Best example I can give is hold a bike wheel by the axel and spin it. The direction it spins is where the force is applied typically up and to the right slightly, most barrels I believe are rifled clockwise. So the bullet will have a tendency of up and to the right. This is fixed by adjusting your sights to the point of impact on your target