If I could only have one rifle it would be in 25-06 Caliber.
From prarie dogs to elk/moose....................75-85 grn bullets for varmints/predators and 115 or heavier premium bullets for Elk/Moose.
It would be a heavy sporter or light varmint contour barrel (just heavy enough to be free-floated). I do way more prarie dog and predator shooting than elk or moose hunting, If I didn't have to include the small varmints, perhaps it would be a larger caliber to reach out further on the bigger game.
It wouldn't be a heavy barrel/heavy stock however (I've had one like this). It worked great for the prarie dogs on windy days, but got really heavy for walking the rough country after mule deer. I've currently got a sporter weight 25-06 and it's perfect for walking and shooting quickly or unsupported, but too much recoil for alot of shooting in the dog towns, not as accurate as the heavy one was either (hope to have Nesika Chad remedy that part soon though).
Remington action or custom action, either one...as long as it can be fitted w/ a jewel trigger. Good Recoil pad too, because 100 rounds a day at pasture pooches can be a little hard on the collar bone (85 grn. bullets at 3600' / sec.)
Some of the fast 6mm's would qualify for the "only one rifle" too, but in order to shoot 115 grn bullets through them; they need a fast twist barrel.......may not shoot the really light bullets as good?
The purpose I guess would have to be everything since you can only have one rifle. For myself, I would probably pick a 26" varmint barrel 308. I could shoot everything from mice to moose, it could reach out quite a ways on large game, but most of all it is cheap to shoot, so I could still get out to practice quite a bit. This caliber is excepted in most competition shooting events, so you could also compete if you were into that type of thing. Just to many pluses. I would chose a Remington or Savage action for the after market support, that is becoming more and more important to me as my shooting advances.
A Winchester Model-70, 300wsm. Not too big for anything, not too small for anything, and very eficient. Also great for near or far on most anything, and the 30 cal has the biggest selection of bullets from big to small.
Next would be an -06, followed by a 338 win mag/ They would make exelent do all rifles as well.
But I do like FEENIX's answer too Good call
"Its not Rocket Surgery.....'
GOD,GUNS,&GUTTS MADE AMERICA, LETS KEEP ALL 3!winmag
"I have No idea why that cop made me ride in the back seat, when I Clearly called Shotgun!"
M700 in .270 or -06. Reliable, reasonably accurate, rugged, and you can find ammo almost anywhere.
Unless I lived in AK, then it would be -06, 300WM or .338WM. Still in M700 though.
For years the M700/.270/Burris 2X7 was my only rifle. Three round zero check, and it killed everything I pulled the trigger on, out to 400 yds. Many deer, a couple of 'lopes and a few elk filled the freezer during those years.
Right now I would go with the 270 WSM that I currently shoot but I would need a 12 pack of barrel to go with it, it's so dang fun to shoot that I kinda wear the barrels out. I shoot 110gr V-max and 110 TTSX and 140gr Bergers and Accubonds, varmints to long range elk. It's almost painful to think about just having one!!
High Fence, Low Fence, Stuck in the Fence, if I can Tag it and Eat it, it's Hunting!