Well, I've only taken about 70 or so Saskatchewan deer, but I would feel fully confident with a .243, or .250 Savage or .257 Roberts with good bullets. I usually have used something bigger because a lot of our hunting overlaps with moose, elk and bear seasons. I do not know one single local hunter who chooses a 300 magnum for whitetails, although a few do shoot 7mm Remington mags. Far more common are .270's, .308's, 30-06, 7mm-08, etc. etc.
A 25-06 is about ideal for open country whitetails in my opinion. Choosing a 300 magnum for any deer-only hunt seems kinda silly to me, besides being a little disrespectful to all that good venison. But if a visiting hunter wants to use a 300 mag and can shoot it well, they kill deer very effectively, that's for sure.
I'm with you on this one. It always puzzles me how the guy who has hunted here once or twice, or even once every 5 or 10 years, seems to know what it takes to kill our deer (AB, SK, etc) better than the guy who lives here and kills 2-3+ deer here every year, some of them real whoppers.
A .30 Mag will certainly do the job on SK or AB deer, about like a .416 Mag will do the job on elk. But, having been on the guiding end of things, I always chuckle when a camp full of non-residents is absolutely convinced that anything less than a .300 Magnum, or even a .270, is asking for trouble, when I've seen so many of our deer pile up like a sack of hammers, often with full penetration and exits, to decent bullets from the .243, .25-06, etc. If you just want to bring your .300 Magnum because you like it, by all means it will do a bang up job, but don't try to tell me that it will kill deer any better than a .243 with 80gr TTSX or 100gr PT, assuming decent shot placement for both. I've seen good and bad situations arise from both classes of cartridge, mainly depending on bullet selection and placement, rather than chambering. Guys who have shot a decent number of deer with both a .300. Mag and .243 will tell you to pick a reliable bullet and put it where it needs to be, and for the most part, ignore the headstamp. Deer are just not that hard to kill.
Confidence in a familiar rifle will do you far more favours than buying a shiny new .300 Mag because you think your old .257 Bob is too small.
