Mr_Flintstone
Member
You are correct about the pressure. Some powders burn more completely in shorter barrels. These rounds used in a carbine or rifle will peak early and then the bullet will stop accelerating (or even start to slow down). Other powders like IMR4227, 2400, and H110 when used in a revolver will still be burning powder when the bullet exits the revolver barrel, and you’ll lose some of the powder’s effectiveness in a big fireball out the end of the barrel. You might get the same peak pressure in each situation, but completely different outcomes depending on barrel length.The only real difference in the data is the reported higher velocity from the longer rifle barrel. The cartridge is still loaded to the proper pressure for the .357 Magnum.