what about a buffer of some sort were the bolt stop is on the custom trunion?? then perhaps mild steel could be used or aluninum would be possable for the trunion and possably the carrier if the weight could be added or in a 22LR build? hardend hammer activater could be added as well. . those CZ 52 extractors dont look bad for around $15.
ill look into the beretta stuf as well. I have a idea for my own design as well If I got to make a entire bolt from scratch Ill just make the extractor as well or possably use a AK design. if a plunger ejector was added then you could use some key stock for lower rails and mill wider groves in the bolt/carrier and then eleminate the guide rod posssably. this would rule out a standard NDS 3 reciver un less you removed the ejector tip and kept the slots thin. but it would work good on a bent flat