I have been following the Big Bore-Terminal Ballistics thread with interest. I am curious to understand the relationship between bullet bearing surface, pressure (initial and sustained) and the resultant impact on velocity. Am I correct in thinking that reduced bearing surface of the bullet i.e. grooves reduces the initial pressure spike after ignition? As the bullet progresses down the barrel and the volume increases the pressure drops. How does this sustained pressure section of the curve look with the grooved bullets? Grooves have been designed to allow the metal to displace rather than compress. If we suppose the baseline bullet has a 1" bearing surface, has a comparison been done on the curves generated by a grooved bullet with a 0.5" total bearing surface and a bullet with a continuous, total 0.5" bearing surface? Is it correct to suppose that as the total area under the pressure curves decreases the velocity of the bullet decreases or is there a different relationship for the area under the initial pressure spike and for the sustained pressure as the bullet progresses down the barrel?

If we operate within the safe margins of a firearm and have utilized the available case volume what are the benefits of utilizing a grooved bullet if we end up losing velocity?

I realize this is a mouthful but would appreciate any feedback or the direction towards a source which could provide the answers.

Eric

pressure is relieved from less friction,
by engraving the lands easier and by not using forward momentum to get the bullet spinning.
if the grooves are not present you are trying to engrave the whole length of the bullet.
you don't lose velocity you are losing pressure which can be made up more efficiently and safely with gas volume.
my take on it anyways.

what Lamar said. Barnes bullets had problems early on with high pressure and with barrel fouling, till grooves were put in the bullet design. Reloaders would use loading data for lead core jacketed bullets, when loading the Barnes. This produced blown primers & worse, as Barnes did not have there own loading data at the time. Today, there are many different bullet designs. Thicker jackets, different copper alloys, lead cores of as many as 4 different alloys (Sierra),& Bearing surface. Barnes History