I have used a 29g needle to hit them. Not bad at all, you get a case of the nerves the first time though.
Also, you dumbasses injecting high volume into that muscle are going to be regretting it down the road. That is asking for trouble. My arms tape out a hair shy of under 20" and I am in the single digit BF. So that should tell you the size, and I don't do more than 1cc in each. Adding more volume to that muscle especially for you guys with smaller muscles is just begging for that muscle to risk rupturing and tearing when you train.