30-06. I used them for years, Springfield custom sporter, Model 70 Winchester, Model 77 Ruger. Always used 180 grain loads because I hunted brushy country. Never lost a deer or elk in the 58 years I hunted.
I noticed someone mentioned the 280 Rem on this post. I have a Kimber-rebuilt 1938 CZ Mauser, originally chambered in 280 Rem. I had it rebored to 280 Rem Ackley Improved, with the blownout straight case and 60 degree shoulder. It sends out the 7 mm bullets same speed or better as the Rem 7mm Mag's do, and burns only 2/3 the powder.
I don't think there's a better cartridge for elk-sized game than that one.
BTW - the 260 Rem (6.5-.308) superlight-weight rifle is incredible!
Well... put the old Enfield back in the gun cabinet in favor of a new Remington CDF stainless, with a fluted barrel in .300wsm. The 180gr SST from Hornaday, driven by 64.2gr of IMF 4350 puts a three shot group in paper that a quarter will cover. So for the elk hunt in October, I'm dialed. Waiting for Mr. Potterfield to send me a .300 shell holder for my trimmer so I can load some Hornaday 150gr sst's for mulies.
I was using my .270 for mule deer with Federal Fusion 150 grain bullets, however have switched to muzzleloader season for deer and shooting Barnes TMZ 250 grain sabots out of my .50 cal Knight Bighorn. For elk season I turn to my trusty Hoyt with Easton N Fused arrows with G5 Montecs.