“the obturation thing” obturate:OBTURATE.
I was visiting a bench rest forum when the subject of gas being faster than the bullet, there was something about flow, fluid and sudden starts, and of course there was that thing about ‘time as a factor’, I casually mentioned a photographer taking pictures at about the same time the trigger was pulled. He did not have a clue what the picture was about. His picture was recognized as being worthy of being included in a book of award winning photographs.
The photograph included a cloud of visible moisture created by compression, a smoke ring, the projectile and escaping gas behind the projectile that ran 90 degree to the bore, with definition, meaning the lands of the barrel could be counted in the gas pattern. Point? Before the photograph everyone thought there was a blast, most of what the photograph recorded was and is not visible. The photo changed the understanding of the events that take place when the trigger is pulled, and time is a factor.
Then there were the curious, the ones that are able to say “I DO NOT KNOW! BUT! I have resources”, sure enough, in a short time it was decided pressure at 10.000 psi +++ has no problem getting ahead of the bullet.
I am the fan of the running start, I want my bullets to have a jump start, I am not worried about hot high pressure, metal cutting gas cutting bullets or barrels, I have more barrels, chambers and bullets than I can ware out,
Then there is the muzzle taper caused by cleaning rods, I tape the joints on old heavy duty cleaning rods, I do not push a cleaning rod, I pull and I make my own bore snakes, it is impossible to jam one up in the bore.
F. Guffey
The photograph was taken +/- a few years of 1912.