Can someone please tell me why this mesh has so many faces?

[BraydenJanak]

so I have this custom ar15 pseudo airsoft lower and have reduced it. on the surface, I would expect this to be something around 5-10k faces, but it's somewhere in the range of 30-70k faces. I have tried reducing it, but is there a way for me to fill it or find out if there are any problems with internal geometries? 

[Steinwerks]

Mostly because of the holes and surface geometry like the logo and fillets that are attempting to keep true to surface curves. I would suggest finding a STEP or parasolid model to work with.

Sorry I rushed to answer the title and not the question! If we use a Section Analysis we can also see the threads are fully modeled as well, which is not helping. This might aid in searching for internal issues as well but nothing pops out at me, although I do my best to avoid STL files at all costs.