Is there any reason why a pre mix bar gun wouldn't work to dispense beer?
Anybody use one? Thoughts?
Pre-mix guns are notorious for getting sticky and jamming up. Beer has all the things that growing bacteria need to settle in and make a mess (which is one of the reasons that FORWARD SEALING faucets are preferred by homebrewers over REAR SEALING).
The parts inside a pre-mix gun are... probably not happy with beer dispensing. Pick your reason: they are delicate, they are balanced for a vastly different product. They are not for beer.
Part of proper beer dispensing, to avoid foaming and flat beer and all the other flaws that can happen from keg to glass, is balancing TEMPERATURE, PRESSURE, and LINE LENGTH
http://www.newbelgium.com/files/Basics%20of%20Draught%20Dispense.pdf
and the pre-mix gun offers several problems there. The input lines for the gun are the wrong diameter (too much back pressure, which requires higher pressure to be used), are poorly insulated (temperature problems), and a gun system usually has very long lines installed (line length).
EDIT: I read this as 'POST MIX' and responded as such. Edited for PRE MIX systems, where the soda comes from a Cornelius style keg, would seem to be a much better candidate... but the above problems (and possibly others) remain.