It was in episode 2 of the OAV, right before Myung was about to be killed by Sharon. You do see Guld in the dark room hacking the computer. So i would say briscojr84's assessment is close. If Guld didn't want Isamu killing him, then the thought of having live ammo during tests would have put a very bright light on the YF-19 team. The rifle was suppose to be loaded with paint rounds/test rounds, and yet the thing fired live ammo. So that would have gotten someone on the YF-19 team in trouble, if not the whole team.