insulin syringes hold at most 100 units, aka 1cc aka 1ml. With gear you will undoubtedly need to be injecting that.
On top of that, using a 28-31 gauge insulin syringe to perform an IM injection is downright STUPID! Insulin syringes were not designed to have viscous oils flow through the needle. Do you realize that you can fairly easily break brittle insulin syringe needles off inside of your muscle tissue?
Good luck explaining that one to the ER physician.