One might consider the % of shots that will hit a 6 inch kill zone in the field at a known 300 yd deer much less if distance is a guess ! I love the old 30/30 but like my old truck , ya got to be reasonable and not over extend it !
Hitting may not be as much of a problem, depending on the particular rifle and the skill of the shooter.
Yesterday my hunting buddy and I were plinking the 500-yard steel plate (about 10-1/2” wide by 14” high) with our Marlin .30-30’s and handloads – his a 150g Speer and mine a 170g Nosler Partition. The plate was freshly painted orange and was laying on the dirt embankment so we could easily see where our shots hit using either rifle scopes or my spotting scope.
OK, we didn’t get any hits. Dave came darn close several times (less than 6”) even though he was using factory iron sights and aiming WAY high – so high that he could no longer see the target as it was obscured by the barrel. I was using a Leupold 2-7x and was placing the crosshairs about 9’ over the target. My shots were consistently missing low but again by less than 6”.
The one time I was at the NRA’s Whittington Center I was shooting my Marilns in .45-70 and .375 Win at the 500-meter rams. Of the last 10 shots taken, 5 with each rifle, 8 toppled a ram – 4 with each rifle. I shoot at clay pigeons at 300 yards often enough with the .30-30 that I wouldn’t bet money on a miss, even though they are less common than hits.
This is not a recommendation to try such shots at game, just an observation that hitting is not necessarily the problem.