Here's the facts: The M-16 and M-16 A1 use LSA lubricant on the bolt and bolt carrier. In the late 1960's, when some dick-headed brainiac on Robert McNamara's staff decided they could save a couple bucks by switching from DuPont stick powder to (I don't know who's) ball powder, the M-16 began to fail constantly. The LSA lubricant keeps the fouling soft enough so that the rifle will continue to function (after a fashion). The consistency of LSA is not that of a typical "grease". The closest thing I can think of that is similar in texture and viscosity is Lee sizing lub.
Oh, and if anyone wants to argue about anything I have written above... stuff it! In 1968, 1969, and 1970 I logged 4,917 flying hours in III Corp. Cu Chi was my home. The Mushroom, Iron Triangle, Michelin Rubber Plantation, Hobo Woods, Nui Ba Den, and my personal favorite #10 place Tan Bien were all in my AO. During that time I recovered far too many body bags, accompanied by muddy and bloody web-gear and a jammed M-16. The M-16 was a poor excuse for battlefield a weapon.