it might be unwise to condemn groove diameter bullets too much.
the brits went down that path with great success, and shot dirty with accuracy at long range,
obviously such shooting requires a chamber to suit, and this would possibly include freebore.
patching to groove and breech seating might well suit some chambers with freebore.
some of the bullet would be engraved in the rifling and some would sit in the freebore.
lubing the patches with tallow and using a serious leverage seater could both help in this process.
keep safe,
bruce.