Barrel heat lot question?

[geberl]

I started out on 1903's and they bear heat lots, when I started playing with garands I noted the barrel markings. I'm assuming they are carrying heat lots as well, I've been keeping track of as many markings as I can. Someone tell me if I'm way off base here.

LMR used A(#) as heat lots
HRA used RS(#) as heat lots
SA Post WWII used A(#)(letter), BU(#), MD(#), Y(#)

If this information is correct then LMR and HRA had only one supplier for their barrels/barrel steel where as Springfield used four suppliers based on the above? This is my understanding of the bolt heat lot theory as being identifyable to steel producers.

I'm also under the impression that the barrel dates were added when assembled rather than when produced? If this isn't correct then when were they added? I've seen barrels with what is the same heat lot (as described above) dated sometimes 11 years apart. All of the other markings are the same but the dates are over a decade different. Most of the "heat lots" vary from a few months to a few years in date but some of the spread is too extreme.

Or am I completely incorrect? All of the information I've gathered from my own personal observations, I've physically held each barrel so I do not feel it is recording errors. I do most certainly thank you for your time.

Information

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