We want to know the speed of a bullet, in feet per second, for a given round. We know the weight of the bullet, volume of the casing, amount of gun powder, length of the barrel, and diameter of the barrel.

How do we calculate muzzle Velocity? Is that enough data or do we need more?

  • $\begingroup$ There are published ballistics charts on various bullets. With a bit of research, you should be able to develop an equation that answers your question. $\endgroup$ – David White Jun 25 '19 at 1:04
  • $\begingroup$ @DavidWhite I don't think that I can by just looking at ballistics charts, they have the actual values for fps and then calculate energy, etc. But I want to know if it's possible to derive the fps without doing tests.. if you knew the weight of the bullet and amount of powder, could you reliably predict the round's fps(velocity) $\endgroup$ – Adam12344 Jun 25 '19 at 1:14
  • $\begingroup$ @Adam12344 probably not without empirical data. I doubt explosions give very precise and reproducible results. $\endgroup$ – electronpusher Jun 25 '19 at 1:26
  • $\begingroup$ You are asking about internal ballistics. See for example this Wikipedia link (en.wikipedia.org/wiki/Internal_ballistics). I only know a bit about ballistics, and not as much about internal ballistics, but I doubt that you have enough information to make a reliable estimate. For example, I believe that propellent burn rate is important in determining how pressure builds up to accelerate the projectile. It is possible you can use the energy and momentum equations to estimate an upper limit for muzzle velocity. A practical result will likely require more detailed analysis and testing. $\endgroup$ – amateurAstro Jun 25 '19 at 1:42
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    $\begingroup$ At a minimum, energy can be lost to friction, the working of the mechanism (gas blowback, anyone?), and left in the gas ejected from the barrel. That’s a lot of places to mess up a BoTE calculation. $\endgroup$ – dmckee --- ex-moderator kitten Jun 25 '19 at 2:06

There are so many variables,I doubt if you could arrive at an accurate figure without empirical data. For a start, the length of the barrel has an important bearing on the muzzle velocity. The nature of the propellant: black powder is seldom used nowadays. The quantity of propellant. The rifling: as well as friction. the rifling converts some of the forward energy into rotational energy. Is the weapon gas operated, recoil operated or bolt action? Are you talking about recoilless rifles (which are not the sort of rifles you can put to your shoulder)? I see you have some of these statistics, but not all.

  • $\begingroup$ When I said you can't put a recoilless rifle to your shoulder,I was forgetting the Swedish made Carl Gustav,which you can put to your shoulder,but you have to keep clear of the venturi. I heard of a soldier who had his shoulder blown off by the blast from the venturi. $\endgroup$ – Michael Walsby Jun 25 '19 at 9:54

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