If you want stop your MS338 or MS700, try to fit this sear in . I have this one in my M28 which is partly VSR10, and it has not slam fire once.
You may need modify the Ares, then again, I don't think anyone is going to make upgrades for it. Even if you get one from Ares, it will be pot metal.
Capital Airsoft sells it.
http://albertaairsoft.com/speed-airs...ear-group.html
M28 cnc aluminum sear set for Echo1 - YouTube