From Q&A section of GG3:
I’m loading for a Remington 700 youth model in .243 Winchester with a 20-inch barrel, with the 85-grain Barnes TSX and a 90-grain Nosler AccuBond. I have Hodgdon H4350, Alliant Reloder 22, and Alliant Reloder 15 on hand. Which would be the best powder? Would the faster RL-15 be better in the shorter barrel?
And John’s Answer On Powders For Short Barrels:
H4350 is one of the most accurate powders in the .243 with bullets from about 85 grains up, and contrary to popular belief faster-burning powders do not provide more velocity in 18-20 inch barrels. This is because all the powder that’s going to burn does so within a relatively short distance in front of the chamber.
A lot would also depend on the hunting temperatures in your country. H4350 is also by far the most temperature-stable of the three powders you mention, but if widely varying temps aren’t a problem, RL-15 would probably result in the least muzzle blast of the three powders, because the powder charge will be smaller. Of course, wearing hearing protection is always smart, but even so less blast tends to help our shooting. This might be particularly true if the youth .243 will be used by an actual youth. Reloder 15 would also probably result in less recoil.
As an aside, if we want to get more kids to hunt, it’s a good idea not to whack a newbie the first time they pull the trigger. And while it’s a good idea for you to do the initial sighting in, they should do the final tweaking. That’s true for kids as well as women (if their husbands/fathers/brothers, are helping them get started). The rifle may not shoot the same for them as for their mentor given their smaller frames, muscle mass, difference in height, cheekbone shape and, of course shooting at paper hurts more than shooting at an animal. That’s just human nature.