You need much more resolution - look at what your total points (vertices) are after you dynamesh. It's better to dynamesh piece by piece, rather than the entire thing. This would give, say, 2million points on a piece of the gun, which gives you much more dense geo all around, rather than spreading out those same 2million…
Turbosmooth it 4-5 times(without isoline display) add an edit poly modifier on top and export. In Zbrush, you separate all the pieces into different playgroups. Use Dynamesh at a higher count (700-1000) and you have even topology. You can create your highpoly there, to bake down on a low poly mesh later on.
@wirrex Just out of curiosity. How would you split a model like this up? I know how to split it up, but in terms of optimal polygroup setup? Also, based on this presumed polygroup set up how have you come to the 700-1000 dynamesh count per piece/group? I assume this is from experience? Sorry guys, I work I work in arch…