303 vrs 30-30 range
It has been my experience that the 303 can when shot accurately has at least a hundred yards more full power reach than a 30-30. My brother has gotten several deer at over 250 yards with a few different 303's and I have yet to do that with any 30-30. He had an old bolt action 30-30 that would reach okay since it had a 22 inch barrel, but still 200 was a stretch. He was a marksman in the Air Force and in the woods.
I have not shot any of the new rounds for the 30-30 such as the Lever-lution or what ever it is called. My brother in law has shot the 45-70 in that ammo and loves it. Three inch groups at 150 yards, 18 inch barrel, offhand, with open sights.
Like our friend said if you have to tote that rifle far, the Marlin is the obvious choice. With a good quality scope set up, the new ammo and of course PRACTICE, the Marlin is truly good for up to mule deer out to probably 200 yards. Maybe more with more practice. I just moved back from Montana and oh yes that reach is important there. If the big toothy critters or the elk decide to fight, then the light fast shooting lever in 45-70 is what you want.
That is of course my opinion, and what others can do might just shame me.
We had this guy bring down a spike in Alabama with a lucky shot with a Winchester 94. Even though two of us paced it off, I will still not tell anyone for it was a LUCKY shot. I could barely see the stupid (and very unlucky) little buck and this city boy pops him in the back of the head. It was as dead as any thing by the time we got to it and maybe one set of prints from where we saw it jerk. Shooting well is the answer to all gun questions.