Thats the older style temazepam gel caps that could be done with. Like the early 90's oldschool ones. If prepared right, it was no more dangerous than shooting oxy, however the ones you are talking about, this cannot be done safely. Listen to the others. Its very dangerous, and many users have indeed lost limbs because they thought they could be injected just like the old ones, but couldn't.
If your so content on injecting a benzo, get the valium amps. They are easily obtainable online, and are meant for injection. They arn't cheap though. Probably buy 10 pills of thesame dose for the price of one amp.
EDIT" ^^^^^ I have injected the the Roche Dormicum 7.5mg tabs. They are freely soluable in water. They have some nasty binders in them, so a micron or wheel type filter is neccessary. I was stupid and used cotton. But I should tell you not to do it. Really the only advantage to I.V'ing benzo's is that they will instantly knock you out. (I barely had time to get the needle out). Really, for the kinds of BA they have, most are above 90%, oral use is the best ROA.