1. Everyone starts off learning 3D by making firearms because they are relatively easy forms made largely from primitives, and they also make you look masculine to your friends who would think you were boring, or just a fag, for making a piece of furniture or a lamp. On the opposite end of the spectrum are people who sculpt "aliens" because the lack of standardization excuses then from making their "masterpiece" from resembling anything, making them immune to criticism.
2. Your gun doesn't loom that good to me. The grip looks bad and there's no trigger. I suppose you've demonstrated that you are able to model, but you should start by making existing objects before making 'fantasy' items to get really good. You know why so many Chinese youths are found to be cheating? Ancient Eastern philosophy holds that to become good at anything, you must spend time emulating the masters. This is why a lot of Asian countries' education is focused more on rote memorization. If I were you, i'd scrap your gun and make an AK or PPSH. Another practical benefit of drawing something already existing is that sometimes, it forces you out of youe comfort zone to use different techniques in order to generate certain unique solids. Doing your own designs right off the bat makes you vulnerable to subconscious bias; you will avoid doing objects you think are outside the software's limitations.
Those are my takes on the matter.