[Pope of Dope]

I have a beer gun that's new.  I'm bottling from keg, and notice that at first the bottles are flat.  Does it take time for the beer to sit in the bottle before they become carbonated? 

I only have one CO2 tank with no splitter, so I put about 10psi into the keg, then attach the beer gun to both posts (using CO2 already stored in keg). I blast with new CO2 every couple bottles or so.

[rob_f]

You're bottling carbonated beer, right? The carbonation won't increase in the bottle unless you've added priming sugar.  With a beer gun you shouldn't lose more than a psi or two of carbonation.  No way they should be flat.  Don't know what to tell you except that a splitter on your regulator wouldn't be a bad investment.