if u use 1 hit, not just in mm/hm mode, in every mode youll get client error soon or later. because its patched by cf team "i think"
simple logic, if u kill someone or many soldier quickly u probably hackin..
in addition to that, -dont know its related with this patch but- if u use 1 hit, and throw someone grenade 2 u "from your team or opposite team", ull instantly die.