7.62 x 39 lovers always like to compare that round to the classic 30-30.
In fact the 30-30 has always used heavier bullets, 150 to 170 grain and the 30-30's bullets were all designed as round nose for feeding in a tubular magazine and for maximum energy transfer into game animals.
The average 30-30 factory load chrongraphs at 2,400 fps from a Win 94 using a 150 grain bullet and 2,200 fps using a 170 grain.
The average 7.62x39 round is 123 to 130 grains and chronographs at 2,300 fps from an SKS or Ak. (there is a wide variation in tolorences with that round and with militray rifles chambered for it)
A 150 grain .308 round nose fired at 2,400fps is still going 1,697 fps at 200 yards. It will still have around 960 ft lbs of energy and will be 7 inch low if the rifle is sighted for 100 yards.
A 125 grain .311 caliber spitzer fired at 2,300fps with be going 1822 fps at 200 yards and have about 920 ft lbs of energy at 200 yards. It will drop about 6.75 inches if sighted for 100 yards with a bullet impact at 200.
So on paper, they would seem to be close, but the 150gr round nose will do more tissue damage and impart more energy into a game size critter.
Oddly enough, the 170 or 180 grain round round fired at only 2,200 fps, will still be going 1,700 fps at 200 yards and have about 1,050 ft lbs of energy. And it will be only 8 inches low at 200 with a rifle sighted for 100.
From experience , I can tell you that a 170 or 180 grain round nose or flat nose bullet with a muzzle velocity of 2,200 fps will smack the heck out of most medium sized game critters within a reasonable range.
When you throw in a longer barrel like a M/94 rifle with a 26 inch barrel and hand loads, then you can push the 30-30 for more range.
Tom Horn used a 30-30 Rifle (not carbine) during his last few years of being a "Range Detective" unlike the model 1876 in 45-60 caliber that Steve McQueen used when playing Horn in the movie.