I have used heroin off and on for 5 plus years. Most recently 2 mintues ago. I almost exclusively snort it now due to an incident that was bad IVing it. I went from sniffing recreationally to using it regluarly sniffing it and deciced to switch to IVing it to make the effects last longer since I was using it so much and $ became an issue. I was scared of ODing so would do as I always do with a new drug, start with a tiny ammt preferring to get NO effect rather than OD or get a bad reaction.
Got comfortable guaging how much to IV and was IVing it regularly. Then deciced I wanted to get the 'rush' people were talking about and how great that felt. Wound up waking up in the bathroom with a terrible pain on the side of my head/face. Turns out what happened is I IV'ed it and immediately fell out and cracked my head on the porcelan toilet, sink, or tub. No one was home as I use in secret. Was glad I woke up but realized that I could have OD'ed and no one would have been there to find me and I would have been found dead a few hours later.
So I went back to snorting. I've IV'ed here and there since that time but do NOT try and get a rush and don't think I ever will again due that experience.
If heroin is active orally, well, it's an option to use that way. But especially since you have experience using opiates and have used high ammt's of oxy, your coming from a different place than someone who has never used an opiate, never a percocet, etc...
When I used heroin for the first time my only prior experience with opiates was like 15 yrs prior using prescribed percocet for wisdom teeth being removed so wanted to be very cautious.
I sniffed a TINY ammt, figuring it's better to be safe and get no effect than use too much. So used like the ammt of a match head from one of those small folding books of matches. Didn't get any effect. Waited like 10 min. No effect so used another dose of same size... did that until I got comfortable guaging how much I could use and feel it.
So what I recommend is using that type of approach, sniffing a tiny ammt and waiting. Then repeating that until you feel it and can guage how much it takes to give you effects and then figuring out the effect level you want (wouldn't recommend you do all this from jump). Get used to it. You might (probably will) 'waste' some in the sense that you will be using too little to feel it the first, 2nd, 3rd dosing with 10 min timebreaks inbetween. But better safe than sorry. After you do this and owrk your way through a bag or 2 or whatever your nervousness about ODing will subside and you will, while remaining safe, get a sense of how much you need to take to feel it.
Then your second go around on another day you won't be as scared (if at all) and will be able to start off with a little more than a small bump.
The dope I used and use isn't as strong as NYC dope so feel free to start off with a bump sooo small you can barely see it, wait 10 min and repeat. Wait 10 min and repeat. Maybe you'll get a good effect from 1/5 of one of the bags you have. But if you start off with 1/20th of on of the bags you have I doubt you'll feel it but you will get comfortable getting to know it and it's effects and how much it takes for you to feel it.
It's well worth 'wasting' 10 or 20 bucks worth of heroin IMO to overcome your fear of potentially od'ing by using tiny, tiny ammts of one bag that will likely give you no effect. Hell, set aside 5 hours and break down 1 bag into as many tiny bumps as you can and ingest each bump 30 min apart if that's what will help you feel safe.
My first time, with only 1 scripted perc experience prior, after using small portions of the first bag with like 10 min breaks in between doses and I started to get comfortable that I had a handle on it so that I would not OD using this method. After the first few bumps with breaks in betwen and not feeling it at all the 'scared I will OD' went away and I felt comfortable working with the substance to find a dose that I would actually feel. That process of taking a dose I would feel but not fall out went quicker as the fear of ODing was now gone.
So then I could do larger bumps and feel something and fairly quickly learned to guage how much I could use and feel it slightly but not be high. Then I transitioned into working to 'get high' while staying safe and not nodding. When I got to that point I wasn't 'scared' of heroin anymore. I should have never used it in the first place, but that's a separate (but not unimportant, to say the LEAST lol) issue.