Yeah, I used to be on OC80s too, the old ones that one could grind up to powder, add H2O, filter, micron filter for safety then shoot.
Never been a huge fan of oxy though really. I'd like to try oxymorphone though, and hydromorphone. But oxy has been a letdown really, there is sod all rush on IV, even with large doses, and unlike most opioids, it has a lot more tendency to make me vomit than others. Also, highly reinforcing, compulsive tendencies to it, despite it being more or less a drug completely lacking in a good reason for that to be the case.
But dose wise, when using them, I'd typically shoot a couple of 80s at a time (bearing in mind tolerance), although I've always vastly preferred dipropionylmorphine personally, as opioid of choice.