on a blow back power feed is better for feeding. balance and view is better with a vert feed but thats about it. closed bolt guns tend to feed better with vert feed due to the ability to vacuum time them.
fatty full body spyder with benchmark frame, the new anti chop bolt and all billet parts by brmachine.
BR Machine rebel-250psi opperation pressure, antichop
Brass Eagle low pressure avenger with esp frame...