I don't think the powder type or bullets really had much to do with the demise of a few of these European cartridges such as the 404 Magnum Schuler. Most of the big bores, although working very well with slow burning powders, do not actually need slow burners to work efficiently. The British used cordite powder for years in most of the well known and very successful big bore cartridges and this is a relatively fast powder. As for bullets, yes there were problems in earlier days with some manufacturers bullets but again all the famous and respected performers on big game, the 375 H&H, 404J, 416 Rigby, 425 WR, 500J, 505 Gibbs and all of the British rimmed big bore cartridges for double guns, gave respectable performance on large dangerous game using the powder and bullets available at the time.

As pointed out by Taylor in his 'bible', The Europeans were always trying to play catchup to the British when developing cartridges and never quite got there, being beaten by a year or two each time. The 9.3 in the various cartridges produced for this calibre was probably the most notable exception to the rule, duplicating the 375 H&H in most respects and being well known and popular in Africa but still never ever approaching the popularity and use the 375 H&H enjoyed.

Of course with the range of powders and bullets available today any cartridge can be made to perform better to its potential including those old tried and true performers of yesteryear.