I wouldn't buy a new gun to practice with..... unless its the exact same thing you have..... yeah, sounds dumb, I know, and I am sure I will get a bunch of dim witted comments to this statement. You should be practicing with the gun you want to hunt with and with the rounds you want to hunt with. It will be a lot less expensive to buy good ammo and dial your gun in than buy a new gun, scope, pod...……… you get the picture. If you buy a different gun and spend all your time shooting it because its cheaper, your muscle memory will adapt to that gun and not the one you want to use. You need to get to know your gun and it be an extension of your self (like a body part).
I am the last person to say don't buy another gun, I a lot of guns, but I practice with the one I hunt with. and I always shoot the ammo that I plan on hunting with. Ammo, if you are not reloading, do yourself a favor and spend the extra $10 a box to get good ammo. I have had a lot of luck with Hornady, (CUSTOM, MATCH, PRECISION..... they all work for me). Some guns like one ammo better than another...….. just got to see what works best with your rifle.
good luck