I’m sure there is a rocket scientist somewhere, maybe even a few on this board that could break everything down to the molecular level, but you have a lot of variables to account for in order to use pure math and science. Tube length, port size, dwell time, ammo, temperature, air density, barometric pressure, humidity, and the cycle of the moon and tides are probably only a few of the first factors involved....(some sarcasm added before anyone comes off the rails over that statement). It’s going to stay locked up until that bullet passes the gas port. At that time there is X amount of pressure built up behind the bullet. The ammo, or more importantly the powder uses in that ammo will be a big factor in this. The size of the gas port determines how quickly the pressure can build in the tube. The dwell time determines how quickly that pressure HAS to build in the tube. Anything can be solved on a blackboard with lots of formulas and better than average chunk of brain between the ears, but experience combined with trial and error will get you to an answer quicker I would bet. Start working on the excel spreadsheet and let’s see where this goes.