Rifling efficiency

[ROMEOHOTEL]

Succinctly stated, is there slippage in rifling?

Does the powder load effect the efficiency? That is, could a load be too 'hot' for the twist?

In measuring the efficiency of propellers, there is the effective pitch and the geometric pitch. The difference between the two is called slip. I reckon the lands in a barrel act in the same (although rifling utilizes rigidity in space (gyroscopic inertia) to achieve the result.)

Just thinking out loud. This is what happens when I think.

[I Swan]

If a load is extremely hot and fast can't the jacket strip out in the rifling? That may not really have anything to do with twist rate also type of rifling may matter some.

[epwegmann]

I don't have an answer for you, but I like that you posed the question. I'd like to hear the answer. Always enjoyed hypothetical things like this.

Succinctly stated, is there slippage in rifling?

Does the powder load effect the efficiency? That is, could a load be too 'hot' for the twist?

In measuring the efficiency of propellers, there is the effective pitch and the geometric pitch. The difference between the two is called slip. I reckon the lands in a barrel act in the same (although rifling utilizes rigidity in space (gyroscopic inertia) to achieve the result.)

Just thinking out loud. This is what happens when I think.

[BeFrank]

Lee has allot of discussion and data on the subject although he relates it to bullet hardness and pressure rather than rifling pitch.
It does seem like a tighter pitch would translate into less velocity and more rotational energy. There is probably a sweet spot for each projectile shape, weight and powder combination.

[Spyder]

There are some barrels which have rifling which is slower to begin with, and gets faster as you go further down the barrel towards the muzzle...

[I Swan]

There are some barrels which have rifling which is slower to begin with, and gets faster as you go further down the barrel towards the muzzle...

Yes, gain twist rifling. I like the concept. The Italians I believe I invented it for some versions of the Carcano. The 460 S&W revolver also has it.

[ROMEOHOTEL]

Who is Lee and do you have a link?

Rifling gain must be a real piece of work. The description reminds me of a ship saw which is a monster band saw used by boat builders to cut bevels in heavy timbers. The arbor tilts (controlled by hand crank) relative to the table to allow cutting a changing bevel smoothly along a timber.

I imagine rifling a barrel with changing twist is more precise but likely the same mathematics involved. Fair to say my interest is piqued!

[Spyder]

First place I ever saw it was on a 20mm barrel out of a ...P38 I think? A buddy has it and the bolt, and is planning on building a rifle when he moves out of state.

[Bob Hostetter]

With true jacketed bullets slippage is very unlikely. In order to get the velocity high enough to strip the jacket you would exceed pressure limits and blow up the gun.

Plated bullets commonly have jacket failure and the potential for slippage increases depending on the hardness of the lead core of the bullet

Lead bullets offer the highest potential for slippage. The softer the lead core the higher the potential.

Having said all of that the likelihood of slippage is very low because the rifling engagement is between two solids. A propeller on the other is a solid attempting to engage with either a gas (airplane) or a liquid (boat). They also have difference slippage potential because a gas can be compressed and a liquid must be displaced or moved.