Do be aware that folk are careless in using ‘dram’ and ‘drachms’. These are very different units. There are 27 grains to a dram but 60 grains to a drachm. It does not help that people for centuries have used the terms interchangeably.
A 2 1/2 dram charge is 68 grains but if you use a 2 1/2 drachm charge you are stuffing 150 grains in your beastie, which may not not be a good plan…….