If one was to actually sculpt most of the weapons used in wargaming figures to accurate proportions all around, rifle barrels would be much thinner, bayonets would be very very thin and the breakage both during casting, packing, shipping and of course when playing with them would be high.
Modern weapons tend to be thicker. Take a look at weapons during the napoleonic wars or before. They are very thin - especially the bayonets.
So in the industry one has to trade off what is practical and playable by altering some dimensions at times.