No, there werent any explosions, you could see the computer burts of a sword, not his rocket SMG, belive me, you can clearly see it's the sword that cuts it. And no, he didn't have that canon then, you can see he only got his sword.
And he went insane when the drugs kicked in, and they do that kinda often....
Ocelots arm fell off right away, it was the blood that came seconds later. So you could really say that he cut faster than they eye can see, cause we didn't see the blood BURTS out until about 2 seconds later....