Made by J.P. Sauer & Son(not a bad thing). It's a Mk V, if you didn't know that. Made between 1959 and 1972.
Don't know how accurate this is, but it's something. http://www.riflemagazine.com/magazine/article.cfm?tocid=1143&magid=81
"...in 300..." .300 Weatherby Mag? Expensive to shoot, if you're not reloading. Shooter's Choice, in Waterloo, Ontario, for example, wants $59.95 per 50 for Remington brass. $84.95 per 20 for 180 grain loaded ammo.
Learn to handload, then you can use any long belted magnum case (H&H length) to make your cases from. Honestly though, I don't get the idea of folks who will spend a "k" or two on a gun and cry about expensive ammo. "I have a Ferrari, and it's great, but the oil changes cost too much". Oh well, whatever floats your boat. - dan