What JohnG said
If there is a lot of dirt/crap you could try the TCT chain. Stihl TCT chains have the carbide on top and come off easily but apparently they don’t make it for 404 anyway. I bought mine off EBay and it has full cutting face carbide so I am impressed. Diamond files are readily available these days so sharpening is not an issue, just remember to sharpen when dulling not when blunt. Also be wary of heat as the chain stretches easily