I think I like M4 better than K390.

[yepimonfire]

I've been using a K390 dragonfly over the last 6 months very heavily at work and just recently started using a Delica in M4 and honestly I don't think K390 is the "M4 killer" everyone makes it out to be for a few reasons.

Both are very high wear resistance steels with excellent toughness and edge stability but in my real world experience cutting dirty stuff full of contaminants they're both functionally similar in how often I have to touch them up and how the edge degrades but when sharpening M4 wins hands down. It takes a super sticky edge that stays ultra aggressive even with a high polish, whereas K390 will tend to get slick and have worse cutting performance if you take it too high. With M4, this results in a major performance advantage during actual cutting because at a high grit it still bites into stuff like zip ties, rubber hose, and straps but also push cuts through plastic, paper, and cardboard like a laser.

Most of us see edge retention/toughness/stainlessness as the major defining qualities of a steel but when it comes time to actually use the knife a better edge cuts better and it's worth sacrificing a small amount of edge retention in my opinion. Some steels seem to have this magical ability to take an unnaturally sharp edge when polished very fine and M4 is one of them.

 

[chalby]

It's hard to compare two different knives like that. The Delica has a longer edge and for the same tasks may work better because of that(and also the thin geometry in general).

I think "M4 killer" is a bit hyperbolic though; they are both great steels if you don't need stainlessness.

Interesting to hear about the different performance for finer grits. I don't tend to go too fine for either of these.

 

[luethge]

Nothing to contribute in a comparison as I have no K390 experience - I love M4 though.. it cuts for a long time, sharpens easily. M4 is great.

 

[Alberta Ed]

I like the M4 in my GB2 -- it takes a biting edge very easily, holds it a long time.

 

[oldmanwilly]

I appreciate and respect your opinion, but I disagree in that I prefer K390 to M4. I had a GB2 in M4 and seemed to have a harder time sharpening the blade, which then seemed to lose its sticky edge quickly. In contrast I seem to have no problem developing a screaming edge with K390 (Police 4, Stretch 2, and Delica 4) and keeping it through rigorous use (cardboard, wood, hide, food, etc.).

Obviously reasonable minds may differ and I agree that K390 probably isn't an anything-killer, but I'd take K390 over M4. That said, I'm glad that Spyderco has put in the effort to offer enough steels that we can debate which excellent steel is better than the other, and none of them are bad.

 

[DeadboxHero]

I've been using a K390 dragonfly over the last 6 months very heavily at work and just recently started using a Delica in M4 and honestly I don't think K390 is the "M4 killer" everyone makes it out to be for a few reasons.

Both are very high wear resistance steels with excellent toughness and edge stability but in my real world experience cutting dirty stuff full of contaminants they're both functionally similar in how often I have to touch them up and how the edge degrades but when sharpening M4 wins hands down. It takes a super sticky edge that stays ultra aggressive even with a high polish, whereas K390 will tend to get slick and have worse cutting performance if you take it too high. With M4, this results in a major performance advantage during actual cutting because at a high grit it still bites into stuff like zip ties, rubber hose, and straps but also push cuts through plastic, paper, and cardboard like a laser.

Most of us see edge retention/toughness/stainlessness as the major defining qualities of a steel but when it comes time to actually use the knife a better edge cuts better and it's worth sacrificing a small amount of edge retention in my opinion. Some steels seem to have this magical ability to take an unnaturally sharp edge when polished very fine and M4 is one of them.

K390 is exclusively MC carbide and should be sharpened accordingly.

M4 has less MC and more of the softer M6C carbides.


Using high performance stones and strops closes the gap.

K390 has more strength, wear and stability in the Spyderco format.

 

[Skar]

I’m with you, m4 seems to perform better for me.
Not sure if it’s the grind verse the actual steel though.

 

[K.O.D.]

I've yet to own anything in K390 yet, but September will be ten years since I bought my GB1, and M4 has treated me well. A member here put a mirror polished edge on it for me at one point, and it's been great. I don't let it get dull, everything sees an ultra fine rod occasionally to maintain a good edge.