I knew someone would jump on that statement, that is why I said "regular U.S. troops". I should have been a bit clearer.
Phil had asked why a rifle that only needed a op-rod change would go through an overhaul/rebuild at Letterkenny in 1965. For the most part I would think that rifles going through rebuilds, in large numbers, in 1965 or so, would be those rifles that had been in storage after being replaced in the active duty military by the M14. Some of those rifles may not have been in need of much work and just had a part or two changed or nothing at all.
Phil also asked why a "unit armorer" would not have changed out an op-rod.
I was also trying to point out that, in the case of these rifles, being in storage and not in active service, they would not have had the opportunity to receive any type of repair at the unit level.
True, Reserve and N.G. units used the M1 throughout the 60s and 70's, maybe longer, but these were not the rifles going through large scale overhauls in the mid 1960s. Joe