Bob, et al. I knew the 12L14 was leaded for easier machineability, it is a LOWER carbon and Mn content, as well and higher sulpher content making it softer than the 1137M. My steel book doesn't say what percentages the "M" gives you. I had a metallurgy course on college about 30 yrs. ago. Time sure flyes!
Does someone have a list of the steels each barrel maker uses? Seems like Jim Chambers posted a list quite some time ago.
"M" means "modified". I would have to defer to a metallurgist for a explaination.
Leaded not softer when subjected to internal pressure. Its not "tough" in this context but brittle.
When steel has Lead, Phosphorus and Sulfur added to make it machine faster the additives form inclusions, stringers etc, in the steel. This weakens the steel especially when subject to internal pressure. Then to further aid machining they are cold rolled to make them brittle so the chips break easily. Doing these things can result in a steel that can be machined 200+ percent faster than a similar hot rolled low carbon steel with less tool wear as an added bonus.
Annealed hot rolled low carbon steel is pretty "gooey" when machined or when threads are cut. Its very ductile as is wrought iron. Good wrought iron is "weaker" on paper than 12l14 for example, but is less likely to fail catastrophically.
Steels like 12L14 may file and machine wonderfully but they well tend to break rather than bend if notched and then struck. Back in the day the common way to cut RR Rail was the notch it with a huge cold chisel with a handle then hit it with a hammer it would break at the notch. This was still common practice in the late 20th century.
Making a steel brittle, adding high levels of sulfur and other metals make it very useful for some things. But its not useful for gun barrels.
The brittle steel problem is not limited to ML barrels. The typical stainless used in modern rifle barrels is a free machining version designated 416 or 416R. This material is prone to failure. But people just love them stainless guns. Krieger's web site states they should not be fired at temps under 0f. Sako had a rash of failures a few years ago and recalled a number of guns. Rifles were bursting with factory ammo. One I saw photos of split full length action and all. I read of a child losing a hand in Europe.
Remington was sued over 1140M in shotgun barrels and lost. Shotgun barrels are subject to flex being thin wall. 1140M will work harden. Over perhaps 10000 rounds or maybe many more, some trap shooters had failures and people were maimed. But 1140M was cheaper than 4140/50 so I suspect some corporate bean counter was responsible for this.
Based on actual tests I know that a 1" across the flats 1137 barrel in 45-70 will contain 50000 psi (White Laboratory). But its still not a good choice if smokeless propellants are used.
The key here is steel quality, a GOOD quality 1010-1018 steel hot rolled is better than leaded screw stock for low pressure barrels and untold thousands of 1911 Colt barrels were made this way (there was a rash of 416 failures here too even though the BRASS CASE is "waste gate" in the 1911 think about it, the barrel many times thicker failed before the brass case did, does this make sense?).
But the material has to be high quality be it 1010 (basically iron) or 4150. THIS is the catch. Small lots of certified steel are not only more expensive they are hard to get in small lots. By small lots I mean 15-20 TONS. By contrast the low quality steel is generally in stock at any supplier and can be bought by the piece. The difference is the things added or not added to the steel, in the care in making the steel and the testing done to check for inclusions and flaws so it can be certified. Mill run steel is just that. They make the stuff, run it out the door and its "good to go".
If this and the letter from LaSalle are not enough then the reader is not going to get the idea anyway.
If I carry on I will simply get into some sort of hot water.
In the rather long discussion in the old Buckskin Report one of the last pieces was written by an attorney. He pretty well ripped the 12L14 advocates looking at it from the liability side.
What the GUN MAKER needs to think about is the modifications they do to the barrels in making a gun from them, vent liners, drum and nipple etc. Thin walled barrels with big openings cut at the breech? We need to look at these past practices when doing thin wall barrels.
The British made a lot of thin wall shotgun barrels with vent liners of one form or another. I suspect they abandoned making large holes in the barrel wall early on since they had a pretty rigorous gov't proof.
Dan
