Guillermo
member
against my better judgement I will repost Grant's explanation
This is the money shot on the subject from a gun expert of impressive renown.
The trouble is that the MIM part is the same hardness all the way through, since that's how it was engineered. This is great for reducing sear face wear, but with hardness comes brittleness - and that thin edge is quite brittle. What you need is a surface hardening of some sort for wear resistance, with the underlying material left softer for strength.
This is the money shot on the subject from a gun expert of impressive renown.