No because "chemical" guns accelerate their loads by putting enormously high pressure gases behind them. Obviously, then, once the load is off the gases spew out the end (and make a really, really loud bang noise). Railguns, IIRC, use a chemical charge to get the first couple of mach but then the magnets to pull the load to full speed so it's not followed out the barrel by a mountain of hot gas.

The flames you see coming out the end are chemical charge and/or bits of the sled melting and it travels down the barrel. (people who know better, please feel free to correct me)