Re: load changes for longer barrel length
Standard load work up, look for pressure signs, as you increase the powder charge with a given case, primer, and bullet.
I nearly blew up my 6.8 using the load I worked up for my 18" barrel in my 24" barrel. It ended up being the powder, I even went below the minimum recommended charge for that powder, and still had excessive pressure. I ended up changing to a more friendly powder. I use the load for the 24" barrel in the 18" barrel now, not a problem.
You have a valid question, and there is concern. Pay attention, have good shooting!
There are only two seasons: Hunting season, and Getting Ready for Hunting season. -DAD