I assume you mean rocking him with shots? If the friend were making threats or coming at you, maybe. But, it also becomes a pretty serious crime at that point. If you're sober, mounted on top of a drunk person, that's making no attempts to hurt you, and you start smashing his face in with fists and elbows, you're probably gonna get hit with some felonies once the cops show up.
With the law it's all about matching the threat. if someone punches you, you can't stab them to death and then claim it was self defense. But if they pull out a knife, at that point you can also pull a blade or a gun because it's escalated to a situation where you can probably argue that you're in imminent fear of your life. So same goes for no weapons. If someone you're thinking MIGHT hit you, so you jump the gun and take them down first and hold them there until they calm down, that seems reasonable. But if you start to escalate and reign down bombs on him, HE could probably shoot YOU at that point if he had a gun on him, claim self defense against YOU, and possibly be good to go. Because you went from 0 to being the attacker at that point, and even though you were drunk and talking shyt, if a world class jiu-jitsu athlete is mounting you and reigning blows down, and you're drunk/impaired, I think you could argue that at that point your life is in danger.
So it gets really gray, really fast, when you start thinking about it also from a legal point of view.