Posted by VernMI on August 11, 2008 at 17:03:02 from (207.69.137.20):
In Reply to: gravity again posted by ken in texas on August 11, 2008 at 16:07:28:
Some excerpts from "Official Report of Vertical Time of Flight for Small Arms Ammunition" (U.S. Army Ordnance Office) expain this.
The firing platform at Miami was about ten feet square. There was a shield of thin armor plate over the heads of the men at the gun. Out of more than 500 shots fired after adjusting the gun so as to bring the shots as nearly as possible onto the platform, only 4 shots hit it, and one more fell into the boat. One of the shots that hit the platform was a Service .30-'06, 150 grain flat based bullet which came down base first and bounced into the water after striking the edge of the lower platform. It left a mark about 1/16 inch deep in the soft pine board. Two more bullets struck in a pail of water beside the machine gun. It was concluded from these tests that the return velocity was about 300 feet per second. With the 150 grain bullet, this corresponds to an energy of 30 foot pounds. Previously the Army had decided that on the average, an energy of 60 foot pounds is required to produce a disabling wound. Calculations indicate that the 150 grain .30 caliber Service bullet fired straight up at a muzzle velocity of 2700 feet per second will rise 9000 feet, taking about 18 seconds to do it; and that it takes 31 seconds to return to earth, the last few thousand feet of the fall being at a nearly constant speed of a bit over 300 feet per second. If this same bullet were fired in a vacuum upwards at the same velocity, it would rise to a height of 113,000 feet. It would take nearly 84 seconds to make the ascent, and exactly the same time to come back, return with the same velocity that it started with.
Source(s): Hatcher's Notebook, by Maj. Gen. Julian S. Hatcher. Copyright 1947, The Military Service Publishing Company. Third Edition, 2nd Printing. April 1966, pp. 510-518
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