You have your metallurgy mixed up.It is not a problem of carbon "burned out", it is a problem of the receiver full hardened all the way through making them brittle ,instead of hard on the outside and soft and tough on the inside.

The people that did the analysis at the time said the steel was "overheated and burned".
What ever that means the actions were not "too hard" but brittle.
Some p[eople feel that since not all the actions were damaged that those that were going
to break have already done so. Many "hard actions were used in WW2.
In any event you have a piece of history, keep it as unmodified as you can.
Good luck!

What is the serial number break point which separates "low numbers" from "high numbers"

From Hatchers Notebook



"While for practical purposes the division between the old and the new heat treatment at Springfield Armory may be taken as reciever # 800,000, this cannot be considered completely accurate, as it has been said that a few receivers of the old treatment, which had been set aside for some reason were put back in the assembly line after # 800,000."

Irv is correct. Carbon, whether in steel or not, can be oxidized (burned) with application of enough heat.



In the case of the "low number" Springfield rifles heat treating was done by individuals judging the heat of the receiver by looking at the colour of the hot metal. This is about as unreliable a method as can be done.



If the steel is overheated, the carbon is oxidized out of the steel and it is no longer "steel", leaving one with a brittle receiver with (sometimes) some of the characteristics of cast iron.



Unfortunately, trying to judge which receivers this happened to by eye is just as unreliable as the original method of heat-treating.



It is also likely not true that receivers that are dangerous will have all failed by now. Steel, like any other metal, is subject to failure by "fatigue" through stretching or bending. Every time a rifle is fired, its action stretches & flexes. Good steel can stand many, many stretches and flexes. Poor steel will only take a more limited number of flexes or stretches. With a poorly heat-treated early Springfield, who knows when that number is going to be exceeded?



It is quite true that most of the early Springfields were NOT dangerously heat-treated, but it is equally true that some were. Was any particular one treated that way? Who knows? Why take the risk to save a couple of hundred bucks? My vision, face, hands, perhaps life, is worth more than that to me.



Happy shooting,



A.C.



(BTW, even "good" modern actions have design lengths of lives. E.G., Ruger's cast actions for the M77 have a reported design life of 50,000 rounds. That doesn't mean they will fail at round 50,001, but that they are designed to last at least 50,000 shots at full SAAMI max pressure. They may go 5 or 10 times that, but after 50,000 rounds you can't count on any particular further number.)