|All of 13 millimetres long.|
|15mm German WWII Grenadier by Battlefront|
The FED really does render pretty decent detail, and though it is more expensive than FUD, for this sprue of six Lewis Guns and pole-mounts, the difference was only a buck or so.
The trouble with modeling personal weapons for wargames figures is illustrated in the photo of the gun next to a WWII German Grenadier. To suit the figures it really needs to be modeled a bit bigger and a lot more chunky. In true 1:100 scale, it looks far too light and slender next to the figure; more like the proportions of a rifle.
That's something that can really only be determined by trial and error; you just have to find out what looks right with the figures you have.
I may do another sprue of guns in rather more exaggerated proportions for this very reason.