Experiment: Recoil vs. Muzzle Velocity

Re:Experiment: Recoil vs. Muzzle Velocity by trhway on Saturday December 22, 2018 @12:34AM (#18739125)

I agree. Recoil or no recoil, the bullet moves the same in the reference frame of the rifle. Proportionally to the masses ratio, the bullet acceleration is about 500x-1000x the rifle acceleration, thus the speed of rifle reference frame in the recoil case at the moment of the bullet leaving the muzzle would be just about 3-6ft/s - an order of magnitude difference vs. claimed 20ft/s.

Edit: forgot about the powder which as hot gas is subjected to pretty much the same acceleration as the bullet. With the powder being about 2-4x bullet mass it makes the rifle only 150x-300x heavier than the [bullet+powder] and that brings us to the 20-10ft/s of the rifle recoil speed, ie the article claim pretty closely matches the theory.

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Re:Experiment: Recoil vs. Muzzle Velocity by mannykannot on Saturday December 22, 2018 @11:02AM (#18741075)

A good point, but the puzzle is, though, that the author isn't recording those sort of velocities (or, rather, the acceleration that would lead to them) while the round is in the barrel.

Not all the gas reaches the bullet speed. We might guess that it averages half that, but that is assuming, I think, a uniform density and complete gasification of the charge (though with regard to the latter, is there a reason for there being a larger charge than that?)

This argument also suggests that the recoil firing blanks would be a substantial fraction of the recoil with a live round, which is not how I recall it.

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