As I mentioned the Bioavilability of morphine is very low- so when you take 30mg of morphine orally less than 50% of it actually enters your system, and it does so gradually which reduces the recreational effects (while still working as an analgesic) further. In addition MS-contin are specifically designed to be released slowly.
However, just the fact that you get anything (even a weak buzz) means that you're still below what I call the 'codeine threshold' (equivilant to about 30mg morphine), codeine has a ceiling dose of around 400mg at which point it won't get any stronger. Most people who have taken opiates for any length of time, even without becoming addicted to opiates, accumulate a tolerance that makes it impossible for them to get high off codeine and necessitating the use of stronger opiates/more efficent ROA.
This means that 10-20mg IV should provide a decent rush/nod- IV morphine is about 3 times stronger than oral morphine in terms of analgesic equivilancy, but the fact that you're absorbing the entire dose in seconds not over hours (in the case of MScontin) means that it feels closer to 3-5 times the dose, with a shorter duration. I'll stand by my original advice- extract your pill as cleanly as you are able to (use the search engine/internets to learn how to best extract your particular pills) into 3 or 4ml and shoot 1ml at a time until you're happy with how high you are. In addition by breaking up your dose you can 'ride the rush' by having a booster shot as the rush starts to subside.
I also strongly reccomend that you take an antihistamine about a half an hour before you shoot up. Morphine can make you itch like a motherfucker and can also produce unpleasant pins and needles feelings on the back of the neck as well as the vein you shot it into becoming visibly red and irritated in a localised histamine reaction. The histamine reaction that morphine causes is essentially the reason why heroin is more desirable to most people than morphine, even though heroin is just a morphine prodrug.
Even if you only get a non-drowsy antihistamine, it reduces the itches to a manageabe level. Sometimes it can also temper the pins and needles so that they're not painful, but rather like a weird, very pleasurably acupuncture-massage.
Have fun and stay safe!