The .30-30 Winchester round (also known as the .30 Winchester Center Fire or WCF) has been around for 120 years or so, making it one of the most durable rifle rounds of all time. The Marlin lever action rifles chambered to fire it, likewise have been updated constantly since that time. With that in mind, let us look at the more modern loadings that will take your cowboy gun from 1895 to 2014.
This old Marlin Revelations Model 30 can be updated to take deer out to 300-400 yards with the right loading.
Arguably, more deer, predators, and feral hogs have been taken with the .30-.30 that any other cartridge in the country's history. Always loaded in smokeless powder even from the beginnings (Marlin in fact labeled early rifles chambered for the round as being "30-30 Smokeless" so they wouldn't have to put Winchester's name on their guns), the cartridge has typically mounted a lead flat-nosed 150-170 grain bullet. This will in general produce an energy at the muzzle of about 1600-1800 ft. /lbs. This is enough at very close range (i.e. 50 yards or less) to take moose as proven by Canadian rifleman Thor Strimbold who harvested no less than 20 of those huge beasts with one-shot kills using standard 30.30 rounds.
These old-school loads are still tested to be about half that powerful out to 200-yards. As most conservation agencies consider 1000- ft. /lbs. to be the minimum threshold to reliably, take whitetail deer, which makes the standard loading for a 30.30 a two-football field cartridge. Well, there are other options.
If you look at the cartridge size of the 30.30, you will see that it is 7.62x51mm with a rimmed case. This is the same as the .308 Winchester. What makes the .30.30 ballistically inferior to that round is the fact that it has to use flat-nosed old-fashioned bullets for safety. Introduced a few years ago, these 160-grain FTX rounds from bullet guru Hornady use an elastomer Flex Tip pointed bullet that is still safe to load in a tubular magazine rifle without risk of the gun spontaneously disassembling itself when fired.
This gives the 30.30 a much better bullet profile that is accurate at longer distances due to its improved aerodynamics. While they deliver about the same energy at the muzzle as traditional loadings, these pointy-nosed bullets still have over 1300 ft. /lbs. of energy at 200 yards and upwards of a 1,000 at 300. As such, you pick up an extra football field or so at least. They cost about $30 a box, which is a bit higher than your typical Remington green box, but hey, you pick up those extra 100-yards if needed.
Incidentally, they also make a green-boxed Zombie Max load that is the same but with different branding.
Buffalo Bore Heavy
The folks over at Salmon, Idaho-based Buffalo Bore have cooked up a pretty sweet 190-grain loading (not a typo) for the traditional .30-30 cartridge. Using a custom Hawk JFN bullet that breaks 2000 fps from test barrels (they clocked 2071 fps from a 1950s era Marlin Model 336 20-inch saddle ring carbine and 2172 fps from a 1940s 336A 24-inch carbine) these rounds are hot and remain hot at distance. The round is advertised as having a "harder core and thicker than normal jacket, so the expansion is minimal, thus insuring very deep penetration which is needed to break large bones and destroy organs deep inside large game animals."
Ballistics show the Heavy as having 1000~ ft. /lbs. of energy (that magic deer number) at ranges of 350-400 yards, which gives you almost twice the range of traditional ammo and a perhaps another football field over the new Hornady load. The downside? It runs $65 a box.
Nevertheless, these options are out there if you want to put the old Marlin to the test.