Hello Giome its me Lucas
If you look at the thing I circled it shows you that its 224 faces with that alone
if you look here
you will see that its only 56 faces a dramatic difference
we do this to lower the amount of polys in a model so for example if you had that addon in blockland and we were having a 20 person tdm it might be a little laggy or so because of its polys
its to do with memory and the overall theme of blockland in my opinion its best to make the weapon fit the overall theme of the game and lowering the polys helps your model fit into the game while still having less polys
I had the same exact problem with my models and I just want to share this with you