I was a member of a (very small---only about 100 members) Michigan National Guard medical unit in the early 70's---in fact, it was a MASH unit. The unit was issued a few firearms for defensive purposes---about a half dozen .45's, probably about a dozen M1's and maybe 20 or so Carbines. I recall that in about 1970 or 71 they replaced the M1's with M16's----then, a couple of years later, replaced the Carbines with additional M16's. I can also kind of recall going to Summer Camp in mid-70's----(that was near the end of my 6 year enlistment)----and noticing that by that time, everyone then had M16's---there were no M1's or Carbines to be seen. Those Summer Camps----at Grayling, in Michigan---frequently included troops from Michigan, Indiana as well as Ohio---so, I would think that they would tend to be somewhat representative of what was 'happening' around the greater U. S.