The perfect width of many AR's and SMG's are five studs but die to the awkwardness of the odd number people often make them 6 stud which to me is unconfortable but you did a great food making it look identical to the real thing.
Quoting McJanbo Productions
That's one awesome UMP! Could you tell me how wide it is? 6 studs? Oh, do you have more pictures? -Jan
Yes, the main body is 6 studs wide. the receiver and the grip are 4 studs wide, as well as the very top of the gun. The rear iron sight is 6 studs wide, and the rails and front iron sight are 2 studs wide. Mag is 2 studs wide, and the stock is 2 studss wide as well. The stock really should be 3 or 4 studs wide but due to piece constraints I couldn't follow through on that. Hopefully I can take more pics of the magazine and some closer shots; thanks for the question!