It was a direct challenge to Gore and was hardly hollow. Heston didn’t indulge in hollow words. The musket was a symbol for all guns. At the time, in addition to “assault” rifles, there was considerable pressure on hand guns, gun locks making use virtually impossible in an emergency, ammunition limitations, etc.
He should have held up at least a Beretta M9 in one hand and an M16 in the other if it was serious