How many bullets does the m4a1 hold?

Answer 1

Just one in the chamber. Otherwise, it's dependent on how many rounds the magazine is designed for. The norm is 30 rounds, but 5, 10, 15, 20, 35, and 40 round STANAG 4179 magazines are available, as are 90, 100, and even 120 round STANAG 4179 drum magazines.