As for the "effective range" of 30-30, I propose that the answer turns on "maximum point blank range."
Link for various calibers MPBR
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Maximum Point Blank Range is the distance at which the bullet falls 3 inches
below the line of sight. Thus between the muzzle and the MPBR distance, the bullet never strays more than 3 inches above or below the line of sight.
For 30-30 MPBR is about 225 yards.
Zero your 30-30 to strike about 3" high at 100 yards to take advantage of MPBR technique.
Beyond 225 yards, you need to think about hold-over.
And there is the matter of shot EXECUTION.
Most shooters will "pull" a shot low if the shot is poorly executed.
Rarely will a shooter pull a shot high.
So if you are in a hurry, and its a long shot, make it a point to aim at the top of the animal as insurance that you won't "pull" the shot low.
Be realistic about your ability to hold in the field.
You might be Mr. Microscopic shooting out of a Lead Sled off the bench.
But how do you REALLY do in the field? We'll say braced against a tree branch. 4 MOA on a good day. Other times double that?
I've attempted longer shots than I should have in the field. Usually felt foolish over the result.
If the animal is moving, and you can't see the whole animal, and the only rest you can muster is your kneecap, ask yourself....