Yes, I did say that, but also giving her somewhat of an answer she wants. Im not just saying not to do it, actually Im not at all telling her NOT to do it, because I know she more than likely will. Im just saying, "make that right choice" as in try nasal/smoking it first, wait then shoot a little, like someone else said.
Basically I wouldnt just start H with IV, I would try another administration first just so you would know slightly what to expect, as in get a feeling of the drug first. AGAIN, im not criticizing anyone. Just saying she can still IV the same day, but get a feel for it before hand. 8(
Your absolutely right. Everyone preaching to her, when she specifically asked NOT to be preached to... She is only asking for advice; I snorted heroin my first time, and didn't even fucking feel it. I had to shoot it to even catch a buzz. I agree going from weed to IV heroin is ridiculous, but most likely she will be so fucking sick it will scare her away a while, or the shit will be such a low dose/ and weak, it won't give her that great rush that gets you hooked(but most likely it will)
As to your question, we simply cannot help you, as heroin potency varies to the point of being stupid. Technically, 100% diamorphine would simply be unsafe; as even just 10mg of morphine is equal to approximtely 80mg of hydrocodone. Heroin(diamorphine) is even more potent than morphine, so your essentially injecting 20 vicodin.
But guess what? It won't be pure, it never is.(otherwise, everyone with a "one gram a day habit" would actually be beyond help, since they'd be blowing through 2'000-3'000mg of oxy just to equal the heroin). My point here though is not to bag on how shitty most heroin is, but rather, to illustrate the point that we have no clue how potent it is, therefore we cannot tell you a starting dose, other than the fact that if it were 100% diamorphine, then 2.5mg would have you high as hell. So just start low, and SLOW, as you can always take more, but never,ever less.
Also, not to sound like a dick, but if your BF is a heroin veteran, he should have this taken care of. If not, you should question what your doing, though I won't dare preach to you, because I don't care and it isn't my place.
My only real advice is to ask the BF his dose, and then ask him how much oxycodone he has to take to get more or less equal effects. Post that here and we can extrapolate a rough estimate of potency, and an even rougher estimate of your dose, based on the conversion from shitty heroin-punk ass oxy!
Anyway, I wish you luck and have fun! Oh and don't die hahaha!!!
(seriously though, don't die)