I have two, 12" and 14". Use them both to take deer and varmints. Learn your gun, scope and loads. I handload all of my loads. Both of the barrels like the 120grn Hornady V-Max. I took a deer last year with the 12" brl and the Hornady 139grn SST. The factory Federal 120grn flat point will shoot 2" groups at 100 yds just a little high and right of my handloads. I limit my shots w/the 7-30 to around 150yds. It will do more but that's what I used to. My shooting range is 180yds long.
My hunting partner has the 30-30 14" Contender. It shoots the Nosler 125grn BT flat and hard. He took a deer last year and it practically fell on the spot. The 30-30 barrel will also shoot the 150 grn Federal Factory loads good enough to hunt deer out to 150 yds with it.
Don't know anything about the .250 but have heard it is a flat shooter and I know of one guy that took an antelope with one from a custom barrel on his Encore.
Yes, you can buy Thurdy-Thurdy ammo just about anywhere but hell, if you are going on a hunt you have been planning, and you leave your ammo, you deserve to not have ammo and maybe borrow the guides old lever action. If it's lost, that another story. You just have to plan ahead. Take two batches of ammo, in separate bags or shipped ahead of time.
I used to shoot Bulleye competition. When we fly to some of the matches, I shipped enough ammo to compete to someone I knew there or to a gun shop. I would take enough with me on the flight or trip. My pistol might have shot another ammo someone loaded but why take a chance.
I'm rambling now. Get one of the three calibers metioned, if that is what you want, practice, reload if possible and get to know your weapon of choice and shoot straight. Good luck.
Mike