It's hard to say, man, both oxy and morphine are subject to high inter-individual variability. Oxycodone is more potent per mg, but even that varies. Typically, it is 1.5x the strength, so that 40mg oxycodone is roughly equivalent to 60mg CHRONIC oral morphine, but, for some people it is double the strength. And for a small portion, oxy is only slightly more effective, and since morphine's BA is dose dependent, they can even be equi-potent at high doses. But in general, 40mg oxy will be more effective. You would likely need 60mg morphine to give the same effect. However I personally prefer morphine over oxy. I mean 60mg morphine would be roughly equal to 40mg oxy, however I find morphine to be MUCH better for analgesia, at equal doses of course. What I mean is, 40mg oxy would be about the same strength as 60mg oral morphine, however I find the 60mg morphine dose more effective as an analgesic. I mean morphine has a much higher binding affinity than oxycodone, and is just a stronger more reliable opioid. Morphine also provides longer lasting analgesia at high doses(despite oxy having a slightly longer half-life). But remember, chronic oral morphine is roughly twice as potent as acute oral morphine. This is because the BA of morphine increases with repeat dosing(also, M6G, morphine's potent and long lasting metabolite seems to play a role in this as well.) So if the morphine dose doesn't initially cut it, you can increase it slightly, but just be patient, as it will take a few days to reach full strength.
Anyway, it is an individual thing, really, but I would suggest starting with morphine. You should also be able to get oxy ir for breakthrough, so really you will have both. Which is a good thing, because other than methadone(or diamorphine, which you obviously can't get) morphine, with oxy as breath through is the most effective opioid regimen for chronic pain.(And this isn't just opinion, studies back this up, demonstrating that a combination of oxycodone and morphine is more effective, AND has less side effects than an equal dose of either drug alone)
So try to get morphine, with oxy for breakthrough. But whatever you do, DO NOT get the op's(the new OxyContin). They fucking suck, you cannot break the time release, which means even in a case of severe pain, you'll have to wait 3-4h for then to take effect, and literally everyone I know who has been prescribed them hated them so much they eventually switched meds(including people who don't even abuse they're medication) not to mention, they're is a chance you will shit gel, with no effects. MScontin does not have the same problem, and you can defeat time release by simply grinding them down into a powder.
Anyway, sorry for the long post, and good luck!!!
