There is a book "United States Rifles and Machine Guns," by Fred Colvin and Ethan Vall, which describes all of the prcedures for making the 1903 . This book was prepared in the anticipation that more factories would bebuilt to make the 1903 rifle at the time of the beginning of our entry into World War I.
I have been told that this entire book is posted on the Internet. Since I have a copy, I haven't need to check. It may have been reprinted.
Any way the description of case-hareningis as follows:
OPERATION 91 CASEHARDENING
Description of Operation--Packed in new,whole bone, heated to 750 deg. c. (1,382 deg. F.) and heated for 2 12 to 3 hr. Apparatus and Equipment: Used--Brown & Sharpe furnaces for crude oil 10 to 14 lb. air pressue: firebox 30 x 45 in.: cast-steel boxes hold 42 receivers: quenched in oil." page 80
I have a copy of TM 9-2210, War Department, July 11 1942 "Instruction guide SMALL ARMS ACCIDENTS,MALFUNCTIONS, AND THEIR CAUSES,
The mmanual shows what can happens in various circumstnces, but it has no mention of low serial numbered Springields
