I know this general topic has been discussed before, but I have a more specific purpose in mind. I don't want to say too much, but I will say I am working on what I hope is an improved rotating bolt design for M16/M4/AR15 patterned rifles. Although I have never experienced a bolt failure myself, and quite frankly I have not fired enough rounds through an AR15 to expect one, I know they do happen. It seems like the most common failure points people have reported are the locking lugs breaking/sheering off and cracks or complete separation at the cam pin hole. Am I correct in understanding that broken lugs are a result of improper heat treating (hardening went too deep) and cracks at the cam pin hole are simply due to a lack of material at that point? Are there any other "weak spots" on the bolt that are somewhat prone to failure? Has anyone ever had the cam pin itself break rather than the bolt?
I'm also curious to know what kind of a market there would be for an improved bolt. I've heard everything from bolt failure being a rare occurrence to an inevitable event, but it seems like failures are more common with heavily used carbines like the M4 than mid-length or rifle length civilian AR15s. Would you replace your bolts with an improved design if one was available from a reputable manufacturer like BCM, or would you stick with the tried-and-true original design? Does anyone have a strong personal opinion one way or the other?
Lastly, does anyone have a spec sheet for a milspec M16 bolt and carrier? I'd rather go off the actual specs when I get to the design phase rather than taking measurements off a bolt that may or may not be to exact spec.