FMJ's are going to give you a lot of runners even with multiple hits. One of the jobs I've had was controlling feral dogs in Vietnam(rabies problems), many time multiple hits were required even at close range. I've had good luck with 58gr V-max out of my 6mm-204 not exiting, You might want to give the 55gr NBT Lead Frees a try, they have worked well for me but never tried to run them past 300 yards. 62gr VG's have left huge exits on the few coyotes I took with them before I gave up on them.
In .224's I like the 52gr Speer HP varmint bullet, it seems to work at all speeds from 222 Rem. to 22-250. I've also had good luck with 40gr NBT's out of my 22-204 at about 3950fps, pretty much my go to rig for pelt hunting.
Looks like you had a great time, were you hunting with lights or just using ambient light on the snow? Back in MN and WI we did a lot of night hunting on Moonlit nights on the snow.
