Some open bolt guns like the Suomi are very accurate,
the Suomi rate of fire is controled by a check valve in
the end of the receiver, since tolerances are very close
the feed stroke is retarded, also the round fires slightly
before chambering completely.
The great Finnish sniper Simo Haya made many kills with his Suomi.
Kids, remember, the ATF has NO sense of humor and that
you're NEVER too old to go to prison!
My understanding is that Simo Haya was not just a sniper and that a great many of his kills were made in close combat. For sniping I believe he used an iron sighted Moisin Nagant. Still at something like 700+ kills he must have been a phenomenal marksman.