M60 over the deck of USS Theodore Roosevelt (CVN-71) in 2006. The Preliminary variant was formally adopted by the U.S. Military in the late nineteen fifties, though presently it had been only supposed for that infantry. It was called the T161 before it had been adopted (particularly the T161E3) https://hoytmachineguns.com/product/paws-inc-m-16-registered-receiver-with-extras/