In terms of reliability in tough environments, the L85 is vastly better than the M4, although it took a while for this to evolve, initially the L85 in its SA80 form was a piece of crap with many flaws. The modifications to turn the SA80 into the L85 (done by H&K when it was British owned), led to the L85 being somewhat over-engineered, thus it is heavy compared to the M4, but it packs more of a punch than the M4 by some considerable margin owing to the longer barrel. Where airsoft is conc...