Different![]()
That doen't even deserve a response. How many trolls are professional mechanical engineers with experience in weapons metallurgy? Are you one?
I thought not.
From Lee Enerson's book:
How was the U. S. Government Issue (USGI) M14 receiver made?
1. A slug of AISI 8620 steel is cut off from 1 3/4 " diameter bar stock. 2. The steel slug is heated to forging temperature using automatic instrumentation. The
temperature range for forging AISI 8620 steel is 1750 to 2200 degrees Fahrenheit. 3. The steel slug is placed into the impression-die forging press and formed. The raw
forging is created. 4. The hot receiver forging is removed by hand and held while trimmed by machine. 5. The raw forging is then heat treated. It is normalized by heating 130 to 140 degrees
Fahrenheit above the A1 temperature. This ensures the core exceeds the A1
temperature. This causes the molecular structure of the steel to change from ferrite and cementite to 100 % austenite. The raw forging is then air cooled or oil quenched and tempered at not less than 450 degrees Fahrenheit. Normalizing produces a fine pearlite structure with a minimal amount of free ferrite. The raw forging is normalized instead of annealed because it is faster and extreme softness is not needed for the receiver. Normalizing also produces greater strength and toughness than annealing.
6. The receiver goes through broaching operations. Broaching is a simple and rapid means of removing metal. Typical tolerances that are obtained by broaching are + or - 0.0005 " to 0.0010 ". Broaching is usually more accurate and leaves a better finish than reaming or milling.
7. The receiver is machined to produce the final shape. The rifle model, manufacturer and serial number is then stamped on the receiver heel.
8. After all machining operations, the receiver is carburized, quenched and tempered. The receiver is placed in a carbon rich environment and heated to 1550 to 1600 degrees Fahrenheit. It is left in this condition long enough to obtain a case depth of
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LEE EMERSON
0.012 " to 0.018 ". For comparison, the thickness of Boise Cascade 20 pound bond copier paper is 0.0035 " (catalog number OX9001). The carbon surrounding the receiver diffuses into the austenite structure surface. After a specified time, the receiver is immediately quenched in oil. The receiver temperature is reduced to well below the M90 temperature, 650 degrees Fahrenheit, in less than two seconds. This
produces a minimum of 90 % martensite structure throughout the receiver. However, martensite lacks the toughness and ductility desired for the M14 receiver. So, the receiver is tempered at 350 to 450 degrees Fahrenheit for at least one hour. The martensite in the core decomposes gradually to a softer mixture of ferrite and cementite as temperature and time are increased. This change in the core increases the ductility and toughness of the core. The procedure is controlled to limit the free ferrite to 10 % of the core composition. By specifying and adhering to the temper temperature range and time restrictions, the amount of free ferrite is controlled. The resulting hardness and strength is achieved within the desired values.
9. The receiver is air gauged for compliance to blueprint dimensional tolerances. At Springfield Armory, non-compliant receivers were stamped with the letter S and discarded as scrap.
10. The receiver is inspected for defects by magnetic particle inspection. 11. The receiver is phosphate coated. 12. The receiver and other M14 parts are assembled together.