Anotherflapoperator..
I think you're saying almost what I was saying! A properly designed weapon will not fire if dropped for the reasons you state.
The Sten, which I trained on as a boy before the Stirling replaced it, was a cheap and cheerful wartime expedient that any workshop could make. It's still "home-made" in Asia, I believe. It had a sear, of course, but on occasions the only way of stopping it if the sear was very worn was to pull the magazine off.