You could just buy a fast twist .30-06 and learn how to shoot it. A really nice scope is more important than an expensive custom rifle for getting hits at some distance. All of my four box-stock CZ rifles shoot 1/2" groups at 100 yards with handloads. The best custom rifles give little accuracy improvement in the field. They are more about esthetics and personal touches than accuracy as long as you buy a really good production rifle. Shooting at game animals at ultra long range for the sake of shooting them at long range is rather irresponsible. Knowing your quarry and proper stalking or hide techniques would beat a custom rifle any day. Animals like antelope and mountain goats are the ones that need ultra long range shooting techniques a good deal of the time. Deer, moose and elk are not what I would call long range game. I was walking on BLM land today, and got within about 30 yards of a mule deer spiker by just walking up on it, with my dog running ahead of me, in semi-open hill country. If you can't get within 300 yards of deer, moose and elk......the problem might be you.....considering the terrain they are usually found in. I drive up on mule deer ALL the time where I could jump out of the truck and hit them with a rock. What is this thing about needing to make 1000 yard deer/elk shots??? My longest mule deer kill was 300 lasered yards. It pays to know your mule deer territory and the trails they use for travel. It pretty much gets rid of the need for shooting over 300 yards.....which is still a long range shot from a poorly supported position which is common while stalking.
Predators and varmints are candidates for long range shooting, as I don't care if they wander off and die. I would RATHER a prairie dog die in its burrow than outside it. Every coyote is a kill-it-any-way-you-can shot and take any shot you feel gives the slightest chance of a hit. The hyper speed varmint rifles like .204 Ruger, .22-250 Rem, and .243 Win are coyote/varmint medicine, and are good for 500 yard shots, more in the case of the .243 Win. But I would not pick any of those for a big game rifle at any great distance, although all of them are good head shot rifles at closer ranges. A guy in Montana has 32 bang-flops on mule deer with a .204 Ruger last time I talked to him, but he does head/neck shots at reasonable distances and is a crack shot. Another guy I know uses a .30-06 and aims for the middle of the body and turns much of the deer into hamburger and has it wander off a couple hundred yards even after a couple of hits. My brother-in-law once hauled him around on the ranch, got him within 75 yards of a nice buck, and he emptied the magazine of the .30-06 without hitting the buck. Guys like him are in the "I need more gun" crowd in most instances.
Reasonable rifles for deer and elk that go considerable distance are .270 Win, 7mm Rem Mag, .30-06 Spfd......and they are all in the Top-10 selling cartridges meaning ammo is available anywhere you are at. A fast twist .308 Win using long bullets can go the distance, and every 7x57mm Mauser I ever saw was fast twist and could use very high BC bullets for long distance shooting, and then there is the .280 Rem. The last three rifles might not have the correct ammo available in a remote location. Norma is the only factory ammo in 7x57mm that shot as powerfully as max handloads in my experience, and it is $50 per box, and the stash of long range Norma 7x57mm I have (from 1984) is no longer loaded by the factory.
I pick up enough .270 Win, 7mm Rem Mag and .30-06 Spfd brass to never worry about needing to buy brass. What my brother-in-law shoots in his .30-06 Ruger M77 is handloads from brass I picked up. The 7x64mm Brenneke is hard to find brass, but for a handloader the greater selection of 7mm bullets beats the .277 cal of .270 Win. The American equivalent is .280 Remington.
If you are getting a CUSTOM rifle, then the chambering will not be an issue for you, especially if you handload as well. I would go with a .280 Remington or 7x64mm Brenneke with a fast twist barrel. The 7mm bore sits at a sweet spot of power, recoil, killing power, accuracy, for all around use on medium big game that the .277 and .308 cal fall just slightly outside of. You will not find either of these two chamberings in many factory rifles, but CZ and Sako chamber the 7x64mm Brenneke as it is very popular in Europe for long range hunting. There is of course Remington M700 for the .280 Remington.
If I was strictly buying factory ammo, then the .30-06 Spfd and .270 Win are my top picks in all around medium big game chamberings for a bolt gun, and .308 Win in semi-auto. My semi-auto .308 is slightly sub-MOA, so it is reasonably good at distance as well. At reasonable distances, I find the 7x57mm Mauser ideal for my uses, especially considering my chosen bullets, one of which is recommended by Rocky Mountain Elk Foundation......150 grain Nosler Partition......and I only shoot handloads or Norma factory loads in 7x57mm......of which Norma only loads the Oryx bullet at present. The 7x57mm is mightily let down by wimpy factory loads, because of all the old tired military Mausers in use. A modern 7x57mm and max loads are another story entirely, as Jack O'Connor's wife proved repeatedly.
The 7mm Rem Mag steals the show in the USA in 7mm bore, and those other, more versatile, 7mm cartridges get shoved aside except for those who study the situation and hunt down an appropriate rifle and get appropriate loadings. Still, if shooting very long range a good deal of the time, the 7mm Rem Mag is about the most recoil I would tolerate.
My idea of a custom rifle would be to buy a very accurate factory rifle like a CZ 550 with a Mauser 98 based action and then have a killer custom stock made from the best wood blank I could find and save the factory stock for rough duty use. It would still be very reasonably priced and have a top notch single set trigger. My CZ 550 metalwork was polished rather nicely, but CZ stocks often look very plain for the quality of the rifle. Only my CZ 527 Varmint has a matte blued finish. The other three have very nicely polished and deeply blued metalwork, worthy of a very nice custom stock. The CZ 550 bolt is not as floppy as many other Mauser 98 type rifles, and same goes for the CZ 527 mini-Mauser action.
