These look well done to me. I only have a couple suggestions:

  1. Consider your line weights more. They can be an effective way to make the construction feel more solid. You keep the lines almost evenly thin for everything instead of say, adding some weight on the outside contours or facing away from the light etc.

  2. Be wary of proportions. Sometimes in your effort to construct you made the snout rather long and box like more than feels natural. Then again you seem to have fixed that in the later drawings.

Good work!