A .30-06, 180 grain to the various .300 mags. I have used: .30-06, .300 H&H and .338 WM. The .340 Weatherby is my favorite elk cartridge but any of the.300 Mags will do.
You're good with any of them, but I'd up the bullet weight on the .270 to a 140-150 and use a mono metal in the .257. That is just my choice though, if you put the bullet where it belongs regardless of size of that bull, cow, or spike you'll be putting meat in the freezer. Weight retention to me is key on elk so I like to start with a heavier bullet or one as tough as I can get when using calibers smaller than .308. I do however think the #1 .300 H&H sounds the most practical of all.
"keep an extra bullet in your pocket and practice reloading."
Actually, that would be one of the slowest way to reload a single shot rifle like a Ruger #1. Some people use loops on their hunting jacket/shirt, some use wrist cuffs but depending on weather conditions I've used a belt holder with loops and a cartridge in every other loop. Colder weather requires I use a butt cuff, again with cartridges in every other loop, my reasoning it it's easier to pull out another round and less fumbling.
There was an excellent article in IIRC, RIFLE Magazine by Al Miller on speed loading the single shot rifle. He goes into some detail on various methods. If the gentleman who is planning the hunt wants a copy, feel free to PM me with an address and I'll send him a copy.
Paul B.
You guys kill me. A standard .270 over the mighty Roy? You have to be kidding me!! The single shot would stay home, ....actually, I would sell it as I refuse to own one and go buy a Elk rifle. The .257 was Roy Weatherby's go to round for North American hunting for a reason and I have watched my Dad kill Elk after elk with it for over 30 years now at ranges most wont try at all. Not that I agree with that part. The .257 is a fine Elk rifle, load it up with some 110AB's or TSX bullets and watch your Elk drop like flies out to 500 with ease. I just bought a .340 Weatherby and my 7STW will be it's backup. My next rifle will be a .257 Wby for a lightweight packer.
Just a small observation , the 270 with a 140 gr PT andthe257 bee with a 120 gr PT have pretty much identical sectional density's . With the velocity edge going to the bee by an avg 300fps . I think it is pretty much a toss up on which would be the better game getter. I'd lean to which ever fit you better and was the more accurate of the two. The stocks on the sub- moa vanguards fit me good and I like the feel of them so I would personally lean that way . But I would use the 300H&H as the primary rifle in this case , and toss a coin to the back up one.