Again, I think Researcher may have some insight as to what went on way back when these old guns were made. But, my understanding was that makers like LC actually procured different barrel blanks for the higher graded guns and labeled them as such when the source was well known like Whitworth steel, Krupp, etc.. Possibly the lower grades of guns had some ficticious names of the barrel steels?
Remember, this was all before any SAE/AISI or other standards were being used for metals. Each maker had proprietary formulas which may have been close to some alloys today, but not because of a industry standard like today. A lot was based on reputation and customer specification.
I suspect Big Al has some insight into today's metal industry. He's right. 4140 could be open hearth or Vacuum-electro-remelt or probably some other processes I'm not familiar with. We, in the US enjoyed a long honeymoon of extremely good metal supply for many years after WW2. But lately, imports and scrap recycling have brought new problems to the metal supplies here. No longer is the usual "certs" from the supplier good enough for important things. Independent testing is becoming more prevalent out of the need to assure quality.
