I currently have 24 different rifles and shotguns in various calibers including a .50 muzzle loader, 44-40, .243, 7.62x54, 30-30, 6mm, 7mm REM MAG and a .375 WBY caliber Remington Model 1917. What prompted my question is I no longer have enough room in my gun safe to accommodate everything and am thinking of reducing the inventory. Consequently, have to decide what to sell and what to keep along with a possible versatile replacement for those I would sell.
Keep the .375 Weatherby and load it based on game and distance.
Unless you play cowboy games with the .44-40 its hunting utility is very limited, and the .30-30 can do the same thing and have more range. Personally I'd sell them both and get a .35 Remington - it would be my do it all east of the Mississippi rifle. If you also wanted to add moose east of the Mississippi, then a Browning BLR in .358 Win instead.
The .243 and 6mm are redundant, and unless the 6mm has a tight twist sell it and keep the .243. Assuming it's not a heavy barrel, it can be your MO whitetail gun, sheep gun, varmint rifle, and your coyote gun, etc.
If varmints are not your bag (in the OP you said whitetail to brown bear), sell them both and get a .260 Remington.
The 7mm RM and 7.62x54 are also redundant. Keep the 7mm RM. The 7mm RM will cover you when the .243 runs out of steam, and is a good do it all west of the Mississippi rifle.
Or if you really want to consolidate, get a 7mm-08 and sell the .243, 6mm, .30-30, 7.62x54, and 7mm RM.
So...
Plan A: .50ML, .35 Rem .243, 7mm RM, .375 Wby
Plan B: .50ML, 7mm-08, .375 Wby and if you need to shoot some varmints on a regular or high volume basis keep the .243 or get a .22-250.