If if recollect correctly the cordite loaded into 303 rounds was hollow. I thought you could thread some fuse wire through the middle to make a long strand.

Modern powders are either single base (nitrocellulose) or double base (nitrocellulose and nitroglycerin - not sure on the percentages) and have surface retardants. The most common Cordite was nitrocellulose (60%?), nitroglycerin (35?) and vaseline (5%). I think the vaseline may have given it the waterproof qualities. The first type of Cordite had a higher percentage of nitroglycerin but burned too hot and wore out barrels quickly. The vaseline may also provide the retardant property.

There are also a few other types of Cordite made - Wikipedia has them listed.