Before we go on, keep in mind that for reasons stated here and in other articles on the HSG that stainless steel is not suitable for real swords, but is acceptable for short knives and decorative swords that are intended to be hung on a wall and not used. With that said, let's discuss the metallurgical differences of the steels in the 400 series.

440C stainless steel has better edge holding capabilities due to its higher carbon content (about 0.2 percent) than 420C. 420C has a lower carbon content, which makes it thus slightly tougher.

You may have heard of 420J2 - this is the equivalent of "mild steel" but in stainless. 420J2 is extremely stain resistant, but cannot be hardened - even if you heat treat it. This is generally the steel used in the fake Highlander swords selling for $80-90 (see our Sword Articles section). In addition, it will not hold an edge, so in all respects, stay away from any swords made with 420J2.

Now on the more technical side, 420C has up to 1.2% carbon content. There is also a fraction of a percent difference in chromium content than 440C but the effect is negligible.

If properly heat treated, 440C could be made harder than 420 and would hold an edge better. However it is more brittle. In replica swords, heat treating is very poorly controlled, and thus you won't see much difference between the two.

In general, you want to avoid stainless steel for swords, because the chromium content weakens the grain boundaries and makes the steel molecularly weaker than low alloy carbon steel (e.g. 5160, 1050, etc.).

If you have to choose between 440C and 420C, 420C is a slightly better choice in my books because although you can't harden it as much, the lower carbon means that it's a bit tougher, which is what you're aiming for in a sword.