Complex sentence: Firearms sold in most countries are required to pass certain safety tests, particularly a proof test consisting of firing a special high pressure round (proof load) which far exceeds the SAAMI pressure maximum for the round (see internal ballistics).
Split into simpler sentences: Firearms sold in most countries are required to pass certain safety tests, particularly a proof test. A proof test consists of firing a special high pressure round, which far exceeds the SAAMI pressure maximum for the round (see internal ballistics).