I once decided that the .303 had to have been designed by a Royal Commission on the grounds that no one individual could screw up that badly. The cartridge is rimmed, tapered, corrosive, erosive, and with a cupro-nickel jacket bullet. The .30-40 Krag suffered from all those problems as well, but the U.S. was smart enough to get rid of it after ten years.
Yes, but you're ignoring the environment at the time of it's design & adoption.
It was originally issued for use with a lever action single shot rifle. The rim & heavy taper were designed to allow for positive extraction & ejection from that rifle.
1888 was the design date for the .303 British & the 30-40 Krag came a few years later (1892) & was designed for a bolt action rifle with strong primary extraction camming & still the advantages of the rim (for positive grasping with the extractor claw) & the heavy taper (to allow the dirty chamber walls to release the fired case) were still very much in vogue. So much so that U.S. Ordinance copied many of the features.
Corrosive? yes, but what wasn't in the 1890's?
If you separate the product from it's environment you will almost certainly have a distorted view!
Allan Quatermain: “Automatic rifles. Who in God's name has automatic rifles”?
Elderly Hunter: “That's dashed unsporting. Probably Belgium.”