Again, never used a 25ml but have used Luer Lock 10ml syringes with 30G .5" tips attached. Midazolam IS a rush %) , ESPECIALLY if you're shooting 150mg or more!
Such a dose is of course too high for even those with massive tolerances, don't use that as a guideline! (150mg puts me in a semi-conscious state, that perfect dream world however I no longer shoot that much, stay lower still get the rush). They use 7.5mg shots in surgery (sometimes have to use several; e.g. with no tolerance as a young teen took 4 to get me under, woke up at least 4 perhaps 6 times during and needed more

-although this is quite atypical).
The inherent danger to your VEINS with a 10ml (or larger!) is of course injecting too quickly- and in particular with midazolam, even injecting as slowly as possible, is that even 1/3rd of the way in, I've got 50mg midazolam in me and am feeling a really nice rush, it is TRULY tempting to push on the plunger as quickly and hard as possible and inject the other 2/3rds. In fact, if you truly inject at the rate you're supposed to, at that high a dose, you're going to be losing motor cordination toward the end--- that could be ugly

The major "precaution" I took when doing this (not saying it's enough!) is that I'd lift weights, then shoot into a large, very visible vein- didn't like the idea of a tourniquet as wanted to make sure arm totally relaxed no excess pressure.
Although I knew I could do more than 15mg/ml, I also knew the more water the easier on your veins-- of course the large rig isn't easy. I was SO glad to see this post and that it's over 25mg per ml, I don't do right at 30mg but close to. Now I use either 1ml insulin syringes (although I truly like Luer Lok, can suck up solution without damaging needle and adjust bevel line up with grips) and 3ml Luer Lok. I won't usually put 6 x15mg midazolam pills in a 3ml, but rather 5. Less water, so theoretically tougher on your veins, but much more control and going slow doesn't feel like an hour- and honestly, if I want to do 150mg I'd prefer two shots with a 3ml than one with a 10ml, much better for my veins even though "two holes."
Plus as I said lately I'm digging taking a 3ml Luer Lok, doing 2ml of midazolam solution and 1ml of methylphenidate solution. Or can be mixed with pentazacine %) . Figured out my hypotheses were correct, pent works while on bupe maintenance- in fact I believe more enjoyable if on BMT b/c pent's deterent is its a delta agonist (dysphoria), however bupe is a delta antagonist. So I take a third the dose of pent it would take me to get off on it- I don't really enjoy the high, the first part is great as terrific rush feels like full mu agonist even on bupe, however after 20 mins enter dissociative phase- and mix with middy, MPH, or all three together %) BTW, 6 x30mg pills IV of pent produced the dissociation, however if I IV a mere 1 (2 is best) I get the EXACT SAME full mu agonist effects phase and full dope rush, however I DON'T get the dissociative part later :D