That is interesting about the bullet given that it is generally accepted that the Austrian Lorenz rifle was the least preferred of the rifles. If the bullet was solid based then it would not allow expansion like the Minie' bullet, therefore it could not grip the lands and grooves efficiently to induce spin in the bullet that would result in a more stable trajectory. In theory, this coupled with the higher pressure would result in a faster erratic path.

You will never have a consistent muzzle velocity on any weapon system. In addition to the factors you already mentioned, air temperature, powder temperature, barometric pressure, and humidity will impact the powder burn rate and trajectory of the bullet. These factors are taken into consideration on the larger weapons systems today such as tanks, field artillery, and mortars.

I know from experience when I was a mortar platoon leader that I could stand behind my gun line and watch the rounds leave the tubes and ascend to the point of disappearing and they had a muzzle velocity of about 839 feet per second. This depended on what charge we were firing and sometimes the humidty enhanced visibility. Tank ammunition velocity is much, much higher but the round has a tracer on it so most of what you see is a streak of light. I know I have shot my Enfield reproduction and could see the round to a point not hit the target at 300 yards. That is probably because of the nut behind the trigger and not the rifle itself.

I am going to contact the dudes at West Point and see what I can find out from them too. They have one of the collections and they have many of the manuals, studies, etc. I'll let you know what else I find.

Respectfully,

Gerald D. Hodge, Jr.
M.A. Military History - Civil War Concentration.
War Between the States Historian
Historian: 39th Georgia Volunteer Infantry Regiment