If you had to pick one caliber for lower 48 what caliber and bullet would be your choice? If someone didn't have the money to have a "deer" rifle and an "elk" rifle or an "Africa" rifle.
That's a tough one for sure.
The 7mm STW to me is the best all around choice for a single gun hunter ballistically but it's an orphan and it can be difficult to even find brass, much less loaded ammo for it.
The 300wm is the most versatile of all common rounds shot in the country today. You can load it light and fast for varmints, with 220-240gr solids for dangerous game like big bears or with 180-200gr expanding bullets for medium and large game like deer, elk, and moose.
It however I think is going to continue fading into history with the advent of the 300PRC which gives superior performance.
That being the case I'd probably pick the 300PRC shooting 180-200gr Accubond or Accubond LR's.
The Accubond has a lower BC but is a much tougher bullet for punching through tough hides, snow, mud, big bones etc but the ABLR has considerably higher bc's even though it will not penetrate as well as it's predecessor at shorter ranges with higher velocity/higher energy impacts.
The Hornady Interbond is my preferred bonded bullet but it appears they are too busy with all their new whiz bang bullets and rounds to put any effort into even producing them on a regular basis if at all anymore and even after 20 years of people like myself asking them for heavier for caliber offerings in 6.5, 7mm, and .30 cal they just aren't budging.
Then we get into mono's. There are some very good mono's on the market and sooner rather than later all federal and probably state lands are going to be restricted "no lead" you need a reliable mono in the mix as well. For me, the choice in mono's hands down is the Peregrine VLR4 with the Barnes LRX and TTSX following closely behind. Hammer Mono's are building a good reputation as well but I personally have seen too much inconsistency in open Hollow Points to be willing to trust them for my own use. Lot's of people have had a whole lot of success with all three.
If I were forced by circumstances however I would not be afraid to shoot any of them if that were all that was available. There's some others on the market I've not had as much luck with such as the Hornady GMX which for me at least just hasn't shown to expand reliably so I quit shooting them.
There's one other that bears entry into the discussion and that's the Federal Trophy Bonded bullet. I've shot a few of them with great results but not enough to swear by them and I've never been able to buy them as a component to load and experiment with.
If you gave me two choices of bullet I'd stick with one of the above bonded bullets for the reasons stated for large and dangerous game and something like the Hornady SST for lighter, thin skinned game like deer and Pronghorn Antelope to shoot from my slower cartridges like the .260 Rem. Lower impact velocities require a different type of more frangible/rapidly expanding bullet to give the best performance. The SST has been the most reliable for me in that category of bullet. I shot a lot of Nosler ballistic tips many years ago and found it to be a little too frangible and explosive for my needs but a lot of folks find great success with that bullet especially on deer shooting those "double lung" type shots where there's little or no chance of hitting anything particularly hard but shooting a whole lot of hogs with them I wasn't nearly as happy with them as I was the Accubond or Interbond.
So to narrow it down finally.
If limited to one gun, one bullet, 300wm shooting Interbond, Accubond, or Accubond LR for practicality's sake, but my go to bullet for everything is the Peregrine VLR4 because it's the most predictably consistent bullet I've ever shot in anything from the .260 Rem to .300RUM to the .375 Ruger. The only problem with Peregrines is they aren't always readily available.
I've reached out to the owner of the company though to see if I can help him make them more readily available here in the US but we'll have to see.