Thread 64261161

If the bullet had propeller-like grooves on the end, would it spin without rifling?

>>64261161 (OP)
Maybe

>>64261161 (OP)
maybe a little. but there are better ways to make a self stabilizing projectile, like fins or pic related.

>>64261161 (OP)
For that pic you'll only spin the bullet a little the gases impact against the bullet at speed, "static" pressure will level out and the net effect will be thrusting the bullet like normal.
The alternative is something similar to rocket or gyrojets that are caseless munition working as hi-low system, and others.

>>64261161 (OP)
would you?

>>64261219
what about spiral flutes instead?

>>64261169
>>64261183
>>64261219
Thanks for answering
I learned new things

>>64261161 (OP)
Yes. Not from the gas but as a boat tail

>>64261260
I think you need a hole through the bullet to let gas past, or it will just equalise out to static pressure

>>64261219
>>64261431
What the fuck are you talking about

>>64261477
there's about ten thousand pounds of force pushing you left, right now
you don't fly away because there's an equal ten thousand pushing right (equal static pressure)
if you want air to push you have to make a pressure difference

>>64261161 (OP)
The pressure pushes on the ramp and the side of the step equally. There is no net torque. It's a common misconception

>>64261510
I think OP imagined it being a control surface acting on air as it travels, not thinking about the propellant gases.

>>64261510
Can you have grooves that start at the front of the bullet that let air pass through to get spinning any decent amount or would they be too insignificant?

>>64261523
I (OP) just thought the blast might make it spin like a pinwheel

>>64261524
disregard my question i just described a rifled slug like it's some new concept

>>64261491
How do you figure airplanes stay in the air despite there being air pushing them from both under and above?

>>64261510
It doesn't tho. The air will clearly be traveling at an angle after leaving that groove instead of directly perpendicular.

It would be nice if we could induce rotation like a fluid coupling.

>>64261725
>what's a pressure difference

>>64261911
Something that OP's pic obviously generates while flying through air.

>>64261921
it looks like he meant it to spin out of the gunbarrel though; if he wanted aerodynamic spin why wouldn't he put the fins on the front? And why would he draw the charge exploding?

>>64261510
This.

>>64261727
On the angled side of the groove the air pressure will be acting over a larger area, however because it's angled the force which acts in the spin direction is reduced. On the straight side the pressure is acting on a smaller area, however because there is no angle the force is entirely normal (90 degrees) to the surface, which means it isn't reduced at all.
This is a Freshman statics problem.

>>64261524
People tried something like that over a century ago. It didn't work. See: >>64256839

>>64261579
Rifled slugs don't spin worth a shit. Taufledermaus has good high-speed video on YT. A rifled slug spins much, much, slower than one fired out of a rifled choke or rifled barrel. It's not even close. The main function of the angled ribs on a a "rifled" slug is to allow the slug to pass through a choke without causing a pressure spike.

>>64261169
Those stabilize like a diabolo pellet or shuttlecock. The angled fins do not impart spin, but rather are shaped that way to help them pass through chokes.

>>64261725
Airfoils (the profile of the wings) create a lower pressure area over the upper surface, by accelerating air over it, and higher pressure area below the lower surface, which is what generates lift. It is, to my understanding, the main mechanism through which airfoils work

>>64262140
They spin
https://youtu.be/a6-cgW90VmY

>>64262286
They do spin, but that is not what makes them stable. They are stable because their center of mass is in front of their center of drag. They don't spin anywhere near as fast as a slug fired from a rifled barrel does, and they're not any more accurate than other drag-stabilized slugs like Brenneke, Gualandi, BPI thug slugs, etc.