I used to always take my .257 Roberts to back up my 7 mag out west. It paid off for me one opening season hunt when a Simmons (my fault for buying a cheap scope) Whitetail scope went to crap on me. I missed a doe. I didn't understand why as the shot felt so good. Sitting in my motorhome in camp that evening, playing with it, I noticed that when I'd zoom the power, somewhere around 7, the reticule would bobble.
Next day, I took a big doe with my old tried and true .257 at about 200 yards and ordered a decent scope for the 7 sometime later. Took a nice wall hanger buck on that same west Texas ranch few years later with the 7 and the new Weatherby Supreme scope.
Now, I have 3 primary hunting rifles and haven't shot that 7 mag in quite some time. It's a good choice out in the open desert country where a shot can be long, but in the woods, it's kinda out of its element. Heck, I shoot my black powder mostly, now, though I took a spike with my .257 last season.
I think the Mosin is okay for woods hunting, but I'd want optics for west Texas. You should probably buy another rifle just because it's a danged good excuse for one, whether you ever need it or not.
Get an 06 or something with more punch. Heck, it'll work on whitetails and be more appropriate if you ever get to hunt bigger game than deer. Even a .338 wouldn't be uncalled for, really. Would back up your deer rifle and be ready for up to brown bear.
I don't know, often wonder why I have the other two rifles than my .257 which I got from my Grandpa and with which I killed my first deer 51 years ago. I never did get to hunt elk, the purpose of buying that 7, really. But, the simple answer is "because this is America and I can".
But, the back up did come in handy once.