I read what everyone else said. Yes, you can do the cold water extraction, if you are willing to take the risk bungling it and wasting it all. I don't know how long the water will last after you extract, so I was always fearful of mold growing if not used immediately, and it will within a certain number of days, maybe a week or two, from personal experience in something unrelated. You can minimize this by sterilizing everything and using bottled water. Frankly, I didn't want to waste my stuff and was paranoid about messing it up or it not working right, so I took it for pain and now have no stockpiles. But you can try it. Just read carefully about how to do it properly. I am seeing that oxycontin can be considered a "brand name" of oxycodone (not that this is what I think--I always know them as separate--but it does say this online, so check to be sure). Check your labels for if it has acetaminophen to be safe.
Anecdotal cases: my relative tried to OD in this fashion but with heroin added, survived, and is okay, for all intents and purposes. It was a suicide attempt.
To contrast this, a friend of my relative's died in this same fashion, but with heroin added in. It was NOT a suicide.
Also, I died from being drugged. I was given one Xanax with a small amount of alcohol unbeknownst to me. I "lost consciousness" but was really walking around interacting for over an hour before I really lost consciousness, according to eye witnesses. I died. They found me dead and had no idea how long I'd been dead. No pulse, no breathing. They revived me. I had no organ damage and was "fine" for all intents and purposes.
I think it depends. I nixed it out for myself, even though I have died previously on much less. It was not worth the risk in my opinion or the waste of the drugs. (Oh, and I found they DO lose potency despite what the gvt tests said, even in good storage. I noticed a decrease after about a few months, so that made me leery as well.)
Edited: for clarity