Depends on what you mean by "harsh conditions", treblig. The English established quite an empire in sub-Saharan Africa. Ted will confirm that one factor contributing to the unique Darne action is that the French--in the same empire-building mode, in the same part of the world (as well as SE Asia and a few bits and pieces in Latin America)--discovered that in hot, humid climates, paper shells would sometimes swell to the point that break-action guns wouldn't function. The sliding breech gun was the answer to that problem.
Also interesting to note that during the late 19th century, both the British and the Americans ran into problems with their military rifles and the then-new metal cartridges. Both the trap door Springfield and the Martini-Henry had jamming problems. Part of the issue was the metal alloy; part the strength (or lack thereof) of the extractors. But both caused problems for American soldiers fighting Indians and British soldiers fighting Zulus--especially in rapid fire circumstances when they'd get hot. At Rorke's Drift (the battle depicted in the movie "Zulu!"), the guns got hot enough that rounds were cooking off as soon as they were chambered. And NCO's were kept busy clearing jams.
