Looking pretty good! Excellent first effort!
It's hard to tell clearly from the pix, but it seems the wash might not have been applied evenly. That is, some spots look squeaky-clean (where the wash didn't reach), while other spots are very dirty. This is particularly noticeable on the barrel.
When I do a wash, I always check from all angles that I have full coverage. I'm one of the guys who likes to do a wash on top of a flat finish (rather than gloss), so it's important to make sure coverage is complete, or those clean areas will show up. I also use a flat, wide brush to "manipulate" the wash after I've slopped it on the model.
Keep up the good work!