I use the term rebar because it is pejorative. But materials similar to the old “Class C” materials are used as rebar.
Given that a receiver and bolt are such expensive items to make, a modern designer would have a hard time justifying using a low grade material such as plain carbon steel in such a safety critical application.
At least in court. Even a very bad product liability attorney would make anyone look very stupid for not using alloy materials with their higher yield and tensile strengths in a firearm.
I looked at Matweb, and so can anybody, for material properties. I assume the plain carbon steels used in the 03 Springfields are representative of what would be used in other service rifles. You can look in Hatcher's Notebook for exact compositions of a few foreign actions. It is my recollection that the M98 was a low carbon plain carbon steel. P.O. Ackely blew up some M98’s, in his book he claimed that M98 materials were close to SAE 1020 to 1035.
Forty two years at the production start of the 03, and about 18 years after Springfield stopped using class C materials in the 03’s, the Oct 1945 American Rifleman Dope column material experts were calling the materials "just plain carbon steel". Even then they understood just how low grade class materials were.
Looking at data on Matweb, the low carbon steel used in these early 03 receivers "Class C" is not used for complicated parts, unheated it is used for rebar, if heat treated for medium duty shafts, studs, bolts and nuts. I did a composition search and found AISI 1117-1118 steel, which is similar in composition to Class C steel. I could not find something that was just carburized and quenched , I found data for 1 inch round AISI 1118 mock carburized, reheated to 1450 F, quenched, tempered. This is similar to the double heat treatment. The Ultimate strength is 103,000 psi, yield 59,300 psi, elongation at break 19%. For something similar to WD2340 Nickel steel, I found one inch round AISI 4820. For that material, mock carburized, 1450 F reheat, water quench, the ultimate strength was 163,000 psi and the yield strength was 120,000 psi, elongation at break 15%. I have not done an analysis of the M1903, so I do not know the actual loads in the considerably thinner than one inch receiver bridge cross section, but it would appear to me that even the double heat treat receivers have a low yield strength, never mind the elongation.
Today’s receivers are usually made of 4140. For a 1 in round AISI 4140 Steel, normalized at 870°C (1600°F), reheated to 845°C (1550°F), oil quenched, 260°C (500°F) temper, ultimate strength 270,000 psi, yield 240,000 psi, elongation at break 11%
Given that a receiver and bolt are such expensive items to make, a modern designer would have a hard time justifying using a low grade material such as plain carbon steel in such a safety critical application.
At least in court. Even a very bad product liability attorney would make anyone look very stupid for not using alloy materials with their higher yield and tensile strengths in a firearm.
I looked at Matweb, and so can anybody, for material properties. I assume the plain carbon steels used in the 03 Springfields are representative of what would be used in other service rifles. You can look in Hatcher's Notebook for exact compositions of a few foreign actions. It is my recollection that the M98 was a low carbon plain carbon steel. P.O. Ackely blew up some M98’s, in his book he claimed that M98 materials were close to SAE 1020 to 1035.
Forty two years at the production start of the 03, and about 18 years after Springfield stopped using class C materials in the 03’s, the Oct 1945 American Rifleman Dope column material experts were calling the materials "just plain carbon steel". Even then they understood just how low grade class materials were.
Looking at data on Matweb, the low carbon steel used in these early 03 receivers "Class C" is not used for complicated parts, unheated it is used for rebar, if heat treated for medium duty shafts, studs, bolts and nuts. I did a composition search and found AISI 1117-1118 steel, which is similar in composition to Class C steel. I could not find something that was just carburized and quenched , I found data for 1 inch round AISI 1118 mock carburized, reheated to 1450 F, quenched, tempered. This is similar to the double heat treatment. The Ultimate strength is 103,000 psi, yield 59,300 psi, elongation at break 19%. For something similar to WD2340 Nickel steel, I found one inch round AISI 4820. For that material, mock carburized, 1450 F reheat, water quench, the ultimate strength was 163,000 psi and the yield strength was 120,000 psi, elongation at break 15%. I have not done an analysis of the M1903, so I do not know the actual loads in the considerably thinner than one inch receiver bridge cross section, but it would appear to me that even the double heat treat receivers have a low yield strength, never mind the elongation.
Today’s receivers are usually made of 4140. For a 1 in round AISI 4140 Steel, normalized at 870°C (1600°F), reheated to 845°C (1550°F), oil quenched, 260°C (500°F) temper, ultimate strength 270,000 psi, yield 240,000 psi, elongation at break 11%