Complex sentence: Further tests have been done to prove how unsinkable the boats really are, March 2007 a 19' Guardian was shot with 1000 rounds from a Barrett.50 caliber Rifle.
Split into simpler sentences: Further tests have been done to prove how unsinkable the boats are. In March 2007 a 19' Guardian was shot with 1000 rounds from a Barrett.50 caliber rifle.