Originally Posted by Helix_FR
The M&P is a totally different animal internally, its nothing like the sigma and the slides are made of stainless so no rusting. Its of their own design, and resembles nothing of the glock except the striker. The Ruger SR series is closer in design to the glock than the M&P is. The baby Sigma is nothing like it at all and yes, they were junk. APEX kits for them run in the low 100's but much can be done without using the APEX kit at all if you so choose to go that way.
You sure about that. S&W has huge QC issues with their slide finish. They try to use a metal treatment like Glock but if done wrong on stainless metals it makes stainless very rust prone. The process is best sited for regular carbon steel. About half the guys I know with MP pistols have slight to major rusting issues.
Do a quick google on the subject. The carbon steel in XD pistols that get the same process don't rust.