Come on Mike, that's like when the guy asks, how long is a piece of string. Response, twice the distance from the middle to one end.
You have way more new and used cam bolts than I. Measure a new cam bolt and one that's been stretched 6-8 times. Post the dimensions.
I have never measured them. I can just tell you that after X number of times they no longer stay put. I choose to change preventatively every 8 times.