Jon,
If I may, can I offer a suggestion, too? Electrodes with comparable composition but with lower carbon content, may be suitable for certain applications in which it is acceptable when lower joint strength is slightly less than base metal strength. With that in mind, with certain carbon steel and low-alloy steels, type 309 (not 309L), type 312 stainless steel , and nickel alloy (ENiCrFe-3) can be used where lower joint strength is allowed. If using the matching filler for the higher grade (4140) then that is outlined in AMS Specification 6452 (4140). Just adding a little more to what you said. Thanks, buddy.