O.K. nimrods, here's the situation: Let's say you shoot a rifle at S.L. across the screens and the velocity is 2500fps. If you take the same rifle/components to 10,000' and shoot it across the screens, what will the velocity be? Higher, lower, same?
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Posts: 28849 | Location: western Nebraska | Registered: 27 May 2003
The MV will be the same or perhaps a couple FPS faster, but it's down range (retained) velocity will be higher than it was at sea level due to the thinner air (as ALF stated).
Posts: 2124 | Location: Whittemore, MI, USA | Registered: 07 March 2002
...thanks to all. Ken O is correct. I ran the above experiment several years ago with a .308, and very little difference in velocity was noticed. If there were a significant difference, the ammo manufactures would have a REAL problem.
with less dense air for the bullet to expell on it's way out of the barrel,I would think that the pressure might actually decrease.However in any case,the difference would be insignificant.
Posts: 3104 | Location: alberta,canada | Registered: 28 January 2002
Originally posted by KenOehler: The change in muzzle velocity and pressure would be smaller than you can reliably measure. KenO
Thanks, Doc; nice to hear from you.
Now let's get really foolish: What if you submerged the test gun in five feet of water, allowing the barrel to fill before firing? Instictively one would assume the velocity of the bullet would go way down, and similarly, one would assume that chamber pressure would go way up -- one might think catastrophically. I'm sure this has been tried (perhaps Mythbusters?), but does any actual data exist?
Posts: 13263 | Location: Henly, TX, USA | Registered: 04 April 2001
Assuming a 30-06 with a 22" barrel, the combined water and bullet would weigh in the order of 550 grains. You better have some mighty slow burning powder, or the bomb will blow before the bullet gets to the muzzle.
KenO
As it was explained to me many years ago, "I feel sorry for those who think ballistics is an exact science. They just don't understand the problems."
Posts: 55 | Location: Near Luckenbach, Texas | Registered: 09 October 2006
The NRA ran the gun under water test back in the 1960s. If you have the indexes you might find the article and photo. They put a 1903A3 Springfield barreled action in a tank about 4 ft long and fired it. As I recall the result was not as bad as you would think and they shot a hole in the end of their tank.
Myth Busters in one episode shot several guns under water with no problems at all. Even a 30-06 as well as several handguns....As long as thier is no air in the barrel and the firearm is equalized it will work fine....
If you'll check, I think that the Mythbusters test was not firing a submerged gun, but rather firing bullets from a gun above the surface into the water to check penetration (i.e., is a diver five feet under the water in danger of being hit with a rifle bullet fired from above, and the answer is -- in most cases -- "no".)
Posts: 13263 | Location: Henly, TX, USA | Registered: 04 April 2001
Originally posted by Stonecreek: I think I'll trust Doc Oehler on this one.
If you'll check, I think that the Mythbusters test was not firing a submerged gun, but rather firing bullets from a gun above the surface into the water to check penetration (i.e., is a diver five feet under the water in danger of being hit with a rifle bullet fired from above, and the answer is -- in most cases -- "no".)
2 different shows, IOW they did both. IIRC the pistol (9mm) revolver (357Mag?) and M1 Garand all survived, but their old beater 12ga split the tube in the "underwater" test.
Posts: 2124 | Location: Whittemore, MI, USA | Registered: 07 March 2002
Environmental conditions do not affect MV. They do affect downrange ballistics. Temperature of the powder (not air temperature) does affect internal ballistics.
Higher Altitude produces higher velocities , but as KenOheler says minimal with the altitude your describing .
Now bump up to 22K miles high and tell me what the velocity would be if the muzzle velocity of the weapon was 2500 FPS. at Sea Level ?. What would down range velocity be ? how about bullet drop at 500 yards for say a 30 caliber 168 grainer ?. Use those brains !
