Id agree with the others who advise against magnum cartridges for what youve described.
None are really much fun to shoot even with muzzel brakes. I use large cartridges because
i hunt long range with them. Sometimes the extra horse power comes in handy for that purpose.
Ive watched 6 br's shot out to 1200 yds on a nice day with amazing results. Whats not to like about
that if your just shooting for the fun of it. A week or so ago a neibor here was playing around with a
7/08 at that distance. He was doing well hitting rocks with that also.
As for the 7x300 win mag, its a nice cartridge that has been getting more popular because of the internet talk about it.
Years ago when the 300 win mag showed up, hunters here were quick to neck it down to 7mm. What they found was they didnt
gain much over a 7mm Weatherby. The 340 and 300 weatherby cases necked down will provide more velocity. So will the
8mm mag and 300 h&h case necked down and the shoulder changed. The 8mm mag version is now known as the 7 STW.
The 7 ultra mag has a slight edge over the previously mentioned as for velocity.
As for barrel life, used exclusivly for hunting with a few rounds shot at targets each year a barrel can last for a persons lifetime.