These aren't very good to be honest but at the same time they aren't bad. The fact you took time to work out 100 guns shows dedication.
One thing that doesn't show is style or artistic merit as i see you aren't really striving to forge your own style or anything.
And shading is key when it comes to pixel art, just because you dont like it doesnt mean its not necessary. Unless your working on a large scale the biggest part of pixels is compromise through minimal detail achieved by the right colors are perfectly placed pixels.
These guns have no character, nothing that would make me go "i want to puck that up and shoot it when playing a game."
Now dont take any of this as a insult, i think your on the right path here if you just experiment a little and study other pixel art and all that jazz.
Either way its just important to enjoy your time doing it.