5.56mm for the Bullpup, iirc.
@realism debate:
Just because you can fire two deagles at once doesn't mean you get any advantage of that. It's not like it just doubles your rate of fire and how much lead you can throw out before you have to reload - like it is in most games.
If people complain about it being unrealistic they aren't saying that it's impossible for a trained human being to hold and fire two deagles at once (we have two hands, afterall, and it's not like the gun would send you flying backwards...). They are saying that the way it is implemented in a game is unrealistic in 100% of the cases (up to now). If it weren't there would be no incentive to use the two pistols at once because you would be better off using one until it's empty and then using the other one until it's empty.
Artificial features like "decreased accuracy" or other role-playing-game-like nonsense is fine and dandy (and it's better with it than without) but it's not realistic! IF dual wielding deagles were implemented in a game in a way that is almost realistic, no one would use them except for goofing around (which, incidentally, is exactly what happens in real-life...).
How much you want to suspend your disbelieve for a game is totally up to you. I for one, am happy for the unexpected boost in badassery that KF brings to the table in this case, but if you think different that's up to you and no amount of logical evidence will change anything about that either way. Neither ballistic properties straight from wikipedia nor videos of some nitwit on youtube.