Despite its tendency to jam, the Sten Gun's simplicity allows it to operate in harsh conditions with very few probabilities of breakage. And even if one did break, spare parts are more than plentiful.
The Mk 5 was the last iteration of the famous Sten Gun. It shows a tendency towards quality over quantity; the parts have a much better finish, its ergonomics are vastly improved with wooden furniture, its accuracy was improved by adding a Lee Enfield's rear sight, and even a bayonet mount was included.