The figure of 115K PSI ultimate yield would seem to split the difference between 4130 and 4140 and makes sense.

Was this material then used as received from the mill without further heat treat?

That would seem to be the advantage over a simple steel like 1080 which would need a good (and costly) heat treat to achieve a high tensile strength.


"The price of good shotgunnery is constant practice" - Fred Kimble