In This Video He Says He Is Using "Mild" Steel:

[Tim Crosby]

  Scroll over to about 17 minutes into it:

 

 What exactly is "Mild Steel" ? Looks like it is as soft as Lead, either that or the graver is scary sharp.

  Tim C.

[rich pierce]

Ordinary steel from the hardware store. Maybe 1018 but it cuts like leaded barrel steel. If you listen to his breathing carefully you may hear when he’s using a bit of force. Sharp graver!

Added later: I looked it up and A36 is a common hot rolled hardware store steel and 1018 is a common hot rolled steel from hardware stores.

[Hungry Horse]

 Remember the originals were made of wrought iron, not steel. Don’t overthink this stuff. Good cheap modern steel is great for furniture on a gun, as long as it plays no structural part on the gun. And it should cut like butter with a sharp graver.

Hungry Horse

[Bob Roller]

"Mild  steel" can be any steel that has not been hardened.I use cold finished 1018 for triggers and the bars and after fitting and function then I remove the triggers and case harden them.Spring steel such as annealed 1075 could be called a "mild steel" and is easy to work with when making any kind of spring.1144 or "Stressproof" is an extremely easy to work type and I made lock tumblers from it for years.It machines easy like leaded 12L14 and hardens as easy as drill rod.Leaded steels are usually used to make fast production runs of nuts and bolts and a variety of smaller screws.I have said that if it wasn't for the heat it could be machined with a finger nail.
Bob Roller

[Goo]

Talking about how soft steel is I sometimes cut up old damascus shotgun barrels to make into rings and add the damascus to pieces of art jewelry for clients.   The damascus is so ductile that when i splay the tube into a flat sheet I can put it through my hand rolling mill to adjust the thickness.   

[Dphariss]

Talking about how soft steel is I sometimes cut up old damascus shotgun barrels to make into rings and add the damascus to pieces of art jewelry for clients.   The damascus is so ductile that when i splay the tube into a flat sheet I can put it through my hand rolling mill to adjust the thickness.

There are many grades of damascus barrel steels and the better ones were not that soft. The best English machine made damascus was suitable for shotguns shooting smokeless and in fact its still possible to order damasus shotguns in England, if you have that much extra cash laying around. Parker shotgun in the US used this damascus.