studman is right...
Notice I said that this would be how "I" would do it..
However, you certainly can buy some .30 cal bullets and load and shoot them. It is likely you will get acceptable accuracy with little to no leading.
However...you will want to be on the lookout for leading in the bore, or erratic accuracy... those things which indicate poor bullet/barrel fit. If that happens, THEN you will need to go through the slugging/measuring routine.
Generally speaking, if you are .002 over bore diameter, with a moderately hard alloy (wheel weights and such), gas-checked and good bullet lube, you should be able to produce some very good groups.... perhaps not quite as "hot" as jacketed bullets, but that's not a bad thing.