If you had to choose one rifle to hunt everything from antelope to elk, what would it be? This rifle must use components that are readily available. It must also be a caliber that is inherently accurate. No need to waste 600 rounds of 1000 round barrel life doing load development. I want to build a rifle but can't decide what to build.
I'd go with the 30-06. Ammo and components are everywhere, it is accurate enough in heavy sporter or light varmint barrels to hit anything you want, barrel life is around 5,000 rounds or upwards of that, load development is easy, and if you go with a 24" or 26" tube, velocities aren't that much below the WSM. I have a gunsmith friend who shoots a 30-06AI, which will shoot standard 30-06 ammo, and kick out an Ackley Improved 40degree shoulder casing, so if you want more, you could make it an Ackley Improved 30-06. Load development for the -06 has already been done by just about everybody, it will shoot accurately at distance with bullet weights from 125gr to 200 grain, it is not too picky about powders, and has a wide range of powders which will perform in it. With a 24" barrel, you can get around 2775 to 2850fps with a standard 30-06, and another 130 to 150fps with the Ackley Improved chambering. It will do pretty much anything you want it to, from shooting coyotes up to Kodiak bear with the right loads. Its still about the most versitile round out there and still one of the most popular cartridges, so its easy to find pretty much world wide. Hodgden lists several powders that will push 200 grain bullets out of a 24" barrel at velocities ranging from 2575 up to 2650fps, and 165 grain bullets (antelope loads) at 2900 to 3,000fps. 180 grain bullets can be safely driven at velocities ranging from 2750 to 2850fps, depending on the powder used, although the high end velocities are MAXIMUMS and should be approached carefully. Cases, dies, projectiles, powders and loaded ammunition are extremely plentiful, and barrel life is much better than any of the .30 cal. barn burners. Even the 30-06 Ackley Improved is good for over 4,000 rounds at a minimum. I have a Ruger M77MKII that I bought in Germany in 1996 and have put over 3,500 rounds through. It has a light sporter barrel, 22" long, and still puts 5 rounds into about 0.8" at 100 yards. My 03A3 will put 5 into 0.75" with a barrel made in August of 1943. I've put over 2,000 rounds through it and I bought it in Colorado Springs in 1993. I don't know how many rounds have been fired in it since it was made back in '43. If you have to have only one rifle, the 30-06 in a 24" barrel will do what you need it to do, from varmints to big bears, and do it pretty well.