On Sat, 23 Feb 2013 13:56:37 -0800 (PST), clark
wrote:

That steel can get incredibly hard if it gets hot, but the barrels are not very hard at all.

I'm not sure what you mean by that; 4140 softens with heat just like
every other steel.

As for gun barrels, 4140 has relatively high tensile strength even
when tempered at high temperatures (for example, temper at 800 deg. F,
and yield strength is still 120,000 psi).

The result is a strong steel that has high elongation (13%, in this
case). That means it's strong but not brittle; its ductility is quite
high for such a strong steel. It's relatively safe with high chamber
pressures.

That makes a good gun barrel. It has good wear resistance, too.


Why pay extra for tool steel?

4140 is not really a tool steel. It's a medium-alloy, medium-carbon
steel. Because it contains chromium and molybdenum, it will harden
with only 0.40% carbon to a higher degree than, say, 1040 steel.

--
Ed Huntress


TIA