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Registered Member #193
Joined: Fri Feb 17 2006, 07:04AM
Location: sheffield
Posts: 1022
hotcrazyfruit wrote ...
Bored Chemist wrote ...
Without some clever tricks there's a clear limit. If the bullet is moving faster than the molecules of the gas then they cannot catch it up to push on it. That limits things, as I said, to a bit faster than mach 1. Incidentally, this is physics rather than chenistry.
which is where you add MORE, thus increasing the pressure. and increasing the speed of the molecules. to take full advantage of this though, you need a longer barrel, so the pressure has more time to increase the velocity, and expand.
Using more gunpowder (or anything else for that matter) doesn't make the molecules faster, it just means you reach the speed limit a bit sooner. If you don't know what you are talking about, it might be better not to post.
banned on 5/26/2009 Registered Member #1877
Joined: Mon Dec 22 2008, 02:03AM
Location:
Posts: 147
if they expand in a chamber, they will continue to expand in the confined space, with an extremely small barrel, the molecules will move faster, because of the sustained high pressure. regardless of the expansion rate of the gunpowder. we all know that the expansion rate of gun powder is 1300 meters per second, then how do you explain how a bullet propelled by gun powder can reach a velocity of 5000 feet per second? 9which is over 1500 meters per second) if you dont believe me look up APFSDS on wikipedia. it stands for amour piercing fin stabilized discarding sabot. and if you dont believe that, get a water pump, try a big nozzle and a small nozzle and watch how much further the small nozzle goes, it applies the exact same way with gun powder and guns.
Registered Member #193
Joined: Fri Feb 17 2006, 07:04AM
Location: sheffield
Posts: 1022
Learn some physics. The mean speed of the molecules is proportional to the square root of the absolute temperature. The pressure doesn't come into it.
You say "we all know that the expansion rate of gun powder is 1300 meters per second" why? That might well be the VoD but that doesn't have anything to do with the queston.
If you had read what I posted you would be aware that I know about tricks to get higher muzzle velocities. (I said "Without some clever tricks there's a clear limit. If the bullet is moving faster than the molecules of the gas then they cannot catch it up to push on it. That limits things, as I said, to a bit faster than mach 1.") You can use a large charge so that the small fraction of molecules that are fast enough to push the projectile actually have an effect, but that's not a pressure effect as such.
Telling me to look up your favorite toy on Wiki doesn't alter anythig. Since you seem to know so much about it, perhaps you would like to explain why it would be driven by gunpowder when virtually no other military weapon still uses that rather elderly explosive? If, as I rather suspect, it uses cordite or some such then perhaps you would like to tell us what the VoD of gunpoder has to do with the issue?
banned on 5/26/2009 Registered Member #1877
Joined: Mon Dec 22 2008, 02:03AM
Location:
Posts: 147
Bored Chemist wrote ...
Learn some physics. The mean speed of the molecules is proportional to the square root of the absolute temperature. The pressure doesn't come into it.
You say "we all know that the expansion rate of gun powder is 1300 meters per second" why? That might well be the VoD but that doesn't have anything to do with the queston.
If you had read what I posted you would be aware that I know about tricks to get higher muzzle velocities. (I said "Without some clever tricks there's a clear limit. If the bullet is moving faster than the molecules of the gas then they cannot catch it up to push on it. That limits things, as I said, to a bit faster than mach 1.") You can use a large charge so that the small fraction of molecules that are fast enough to push the projectile actually have an effect, but that's not a pressure effect as such.
Telling me to look up your favorite toy on Wiki doesn't alter anythig. Since you seem to know so much about it, perhaps you would like to explain why it would be driven by gunpowder when virtually no other military weapon still uses that rather elderly explosive? If, as I rather suspect, it uses cordite or some such then perhaps you would like to tell us what the VoD of gunpoder has to do with the issue?
wel. to start you could be a bit more humble about things, but thats not my argument. alot of military devices still use gun powder, if they dont, perhaps you could tell me what they DO use. and even link me up. i know for a fact that the apfsds round uses gun powder. increased pressure has all to do with muzzle velocities. if the expansion rate of a substance increases, it only means the pressure builds faster. like i said, with a longer barrel, it would allow more time for the gases to expand, and push the projectile faster as it goes down the barrel. now im tired of arguing. good day.
Registered Member #193
Joined: Fri Feb 17 2006, 07:04AM
Location: sheffield
Posts: 1022
Slightly ironicaly this site shows that they use a nitrocellulose (pyroxylin) based propellant for their apfsds, but they call it gunpowder. To be fair, my Russian isn't that good so there's no way I could give a better translation the other way. There's no way that the reddish brown stuff is gunpowder which is black.
banned on 5/26/2009 Registered Member #1877
Joined: Mon Dec 22 2008, 02:03AM
Location:
Posts: 147
Bored Chemist wrote ...
Slightly ironicaly this site shows that they use a nitrocellulose (pyroxylin) based propellant for their apfsds, but they call it gunpowder. To be fair, my Russian isn't that good so there's no way I could give a better translation the other way. There's no way that the reddish brown stuff is gunpowder which is black.
BTW. those are tsnk charges, apfsds rounds i was talking about are 15mm and travel at 1900m/s
Registered Member #193
Joined: Fri Feb 17 2006, 07:04AM
Location: sheffield
Posts: 1022
The last line or so says "4Zh-63 (DOI UNKNOWN) New high-energy propellant that allows to increase APFSDS muzzle energy by 5% over the previous charge models. ".
Registered Member #193
Joined: Fri Feb 17 2006, 07:04AM
Location: sheffield
Posts: 1022
BTW, hotcrazyfruit, I'd still like to know which branch of the military thinks its a good idea to send up a big cloud of smoke to inform the enemy of exactly where you are firing from (ie to use gunpowder). I have friends and family in the armed forces and I'd like to tell them to avoid that particular bit of the military. Thanks
Registered Member #16
Joined: Thu Feb 02 2006, 02:22PM
Location: New Wilmington, PA
Posts: 554
Play nice kids.
This does not speak particularly accurately to the actual speed limit attainable with 'gunpower' in particular, but it does speak to the technological and physical challenges in reaching this max velocity.
To my knowledge, the fastest commercially produced center fire, man portable rifle to date is the .22-.243 at a blistering 5275 FPS, or 1600m/s. This was a custom load on a modified rifle shooting a very light round, but it still counted as commercially produced (Thats what you get when you stick a 35gr projectile sitting on top of 60+gr of high velocity powder).
The fastest 'over the counter' ammunition currently available is the Ruger .204 which regularly tops 4,500 FPS, and has been clocked above 5,000 FPS with custom loads.
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Speed Limit of GunPowder.
