Looks like you need a good cleaning. I use Gunzilla/copperzilla to clean the barrel. Alternatively, soak the bore with WD40 for at least 30 mins, few passes of bronze brush, soaked patch and finish with dry patch. Ballistol is also a good non-toxic bore cleaner/CLP. However, I find gunzilla/copperzilla to have the right strength in cleaning the bore in less time.