Originally Posted by
In Absentia
531 is basically the same as 4130. 631 is an improved version of 531, so it's probably not much better than 4130. At least not enough to base a purchase decision on.
Reynolds 531 is not 4130, and Reynolds 631 is DEFINITELY not 4130. Reynolds brand names (531, 631, 853, 753, etc.) all refer to both a specific model of tubings, and the specific materials used to make them. Some are available in a variety of thicknesses and butting, and some are not. They are brand names.
4130 is a material. It is a specific composition of steel. It is made into tubing by a number of manufacturers in just about any thickness, butting, etc. that you can think of.
As I understand it, Reynolds 520 is generally referred to as standard double-butted 4130 steel.