Start with 2 ml, then work up to 3 if you are worried, but plenty of people shoot 3 mls all the time.
It is a pretty large muscle.
I can't shoot there becuase I always seem to hit a nerve , I am scared to stick a needle there at this point.
I got sick of getting that crazy sharp pain when you stick the needle into a nerve.
But, there are plenty of people that know exactly where they can shoot it without any problems!
I used to inject into my biceps and triceps in the past, but now I just do shoulders and glutes only.
I mainly do shoulders becuase I have to hide my cycling from my wife, and she always feels around my butt for lumps when I start looking bigger.
She usually can tell I am on within a few weeks, but now I am on HCG all the time and she thinks I am growing from that.
Sorry I got off topic a bit!