ThisI get some of my best speed in my short barrels using the same powders that give best velocity in long barrels.
I understand the premise behind larger calibers using slower powders in longer barrels and overbores BUT, It's not like we are using different powders because of a shorter barrel. Take for instance a 300 winnie or a 7RM...I'm going to use H1k and Tumbo in those chamberings no matter what the barrel length is. Like I said before, powder burn rate makes little difference to me with regards to barrel length. I choose a bullet weight that I want and chamber up according to the horsepower I need to get that projectile to desired speeds. I would deff not be running a long pipe in a 28 Noz because I could likely get a 195 to 3050fps in a short barrel. I see no advantage of running a 28"-30" over a 26". Likely this will only go from 3150fps in a 26" to 3200fps in a 28". But we like numbers and if the numbers you want say run a 30" than you do you. There is no right or wrong answer to this, it's just how you feel personally.