External Link/Members Only reckons an average 3.7ml
I don't know, we are all different, could be some freaky genetics helping our cum master here! But pumping out 5ml every time just seems a helluva lot.
I once saw a WG after I'd saved up for the best part of a week, nearly going mad in the process, managed 3 times in two hours. I didn't measure the volume, but the first two times I came it looked like I pretty much filled the condom.
At the end of the third fuck, it was more like a few drops