As I said earlier,
I really don't think the grain matters as much as the bullet construction and your ability to hit the critter where the bullet will get to the soft squishy parts that bleed a lot.
I use a 240 grain soft point for hunting as opposed to a hollow point. I think the soft point will drive deeper and most likely will pop out the other side and mushroom nicely.
a 300 grain bullet will be slightly longer than the 240 and it will definatly drive deeper into the hog.
Guys here are shooting meat hogs, like in this picture with cowboy loads. (this was shot with a 150 grain all copper bullet from a 308 win - Had to use lead free ammo) no fuss no muss jut a shot in the boiler room and the guide yelled for another one, when he stood up and that one went 1/2" from the first. ) The cowboy loads from a colt 45, 44-40, and 38-40 are about the same as 44 Special. The added energy from the 44 mag helps to drive that bullet deeper and through. but shoot the fastest (with in reason) load you can well. If that is a 44 Special, Hot special, or wimpy mag like the Winchester 210 grain silver tip, or a full house load, you will be much better prepared than having a super killer bullet you stuck in his guts, took off a leg ( I think they run faster on three legs )