think, (not sure books are buried under junk)
that only black powder grenades date back to 1914, black powder having an uneven burn rate was found to be unsatisfactory for explosive filler, hence development of RDX/TNT.
Hey Tony, since you have the materials to be,
ahem, "The authority"

do a comparison of 20mm,30mm,and 75mm shells as far as pene,KE,and explosive force, I don't know enough about aircraft armaments to comment on those, but the 75mm Kwk L48 on the IVH seems a bit weak, in both hitting power and range.
Btw, where can I get your book? always willing to add to collection

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pzvg- "5 years and I still can't shoot"