When you mention the 308 Norma Mag, you can count me in. At last count, I believe I had 5 rifles so chambered, including a Custom rifle built by Leeper.
I've owned pretty well all of the "big" 30's, with the exception of the 30-378 Wby. They are quite capable of doing whatever I need them to do.
Anytime you start driving 180 grain bullets in the 3100+ area, or 200's in the 3000 fps range, you have a pretty effective hunting partner.
I have taken several head of big game, such as Moose & Elk, at ranges that at best could be described as "way out there" lol. Never had my 308NM let me down.
The 300 Wby, is a tad faster, all other things being equal, but burns considerably more charcoal to get there. Not a biggie, of course, but a factor nonetheless.
One other factor that is worth noting, is that, while not quite as widespread as the 300 Winchester mag, The Weatherby 300 is quite popular, and commonly available.
Regards, Dave.