The Human Engineering Lab’s HEL-E4A was the most commonly used suppressor used in the Vietnam War. It was the result of a series of suppressor designs from the Aberdeen Proving Grounds HEL which were developed to balance suppression and back pressure, so that they could operate reliably on a standard M16 rifle. A total of 960 were sent to Vietnam in late 1968 and early 1969 (in addition to 120 earlier HEL-M4 pattern ones). Today they are extremely rare, as very few came back from the war.
The example I am using here is a new reproduction made by International Milspec Co (Intl Mil Co).
if you like Tom Clancy (Without Remorse), there is a pretty good discussion of suppressing a shortened M16 to use a Navy-made suppressor (as well as an account of suppressing a .22 pistol.
I like Tom Clancy, but the man couldn’t write a realistic love scene to save his life. It’s still a good book.
CG