Burrard shows at least one time, pressure, velocity chart but is rather hard to decipher in the early stages. This was taken with the old 33 grain bulk "Smokeless Diamond" with a 33 grain charge (3 DE) & 1 1/16oz shot charge. He did not show the actual pressure rise but simply started it at the peak @ approx 1" from breech. Both time & velocity were showing a very near vertical rise at this point with time at about .0002 sec & vel about 100fps. Max pressure was 2.8 TonSqIn. By the 4" point pressure had fallen to about 2.5 ton, vel risen to about 750fps & time to about .0007 sec. 8 inchs pressure @ about 1.25 ton, vel @ 1000fps & time @ .0011 sec. In the 30" bbl velocith reached about 1285fps, pressure dropped to under .2 ton & time was just over .0026 sec.
I don't know just how this would apply to more modern powders but suspect would be very close to a powder having a medium burn rate, say on the order of Green Dot & similar.
PS; He also stated that upon the powder being ignited the initial pressure rise was on the order of 10,000 tons per second. Of course as the wads/shot begin to move, giving increasing volume, the rise slows, then peakes & starts to fall all in about that .0002 secs. This initial point is of utmost importance & shows why crimp strength can play a vital role in developed ballistics & also why the loaded shell length should never project into the cone, possibly delaying that initial opening. Things are happening "Very Fast".

Last edited by 2-piper; 04/09/07 07:49 PM.
Miller/TN
I Didn't Say Everything I Said, Yogi Berra