Things I've learned.
I've been loading for 20 plus years and at times ,wheather of shear boredom or some learning quest being distracted ,learned that we disagree a lot often. So in no doubt a rambling text I will share some of what I've learned and proved out for myself ,sometimes on paper sometimes in hand ,most certainly misattributed but accurate.
Longer bbls always make a cartridge faster. Well my 38s gain about 50fps from a victory model S&W 4" to a 6" Sec6 and 400 to an 18" Marlin carbine. The 45-70 w/a Remington deference loaded 350gn HP picks up over 300 in a switch from a guide gun w/its ported 20"bbl to a random reproduction trapdoor of 28",taking it from not quite making the legal big game tool to elk slayer. According to published testing using a surplused rebbl'd 1903 in 30-06' the cut at 24" was faster than at 25". The change from 22-24" ,less than 5fps. You know there's a catch ,22LR the 6" Ruger MKII clocked w/in 3fps of my 18" Winchester 190.