Lock and load might be a backward version of apply the safety catch and load the weapon. I guess it just sounds cool. Oz Army commands are a bit more prosaic, Load (put a full magazine on an unloaded weapon) Action, (cock the weapon, on the M16 that included seating the magazine and hitting the magazine assist, on the SLR it includes raising the appropriate sights), Instant, (safety catch to fire) and Unload, (magazine removed, cock lock and look, catch, fire, catch, any discharged round to basic pouch, do up basic pouch. End of drills.
Bit of stuff there as well about the elevation and orientation of weapons when this is being done but thats the gist of it.