You hadn't mentioned if it is a brand new rifle. If so it may have to much lube in the main cylinder.
I didn't know you should use parches with JB bore paste..the instructions say to use a bronze brush. I have always done 40 strokes with the bronze brush, and have had excellent results with this method in my Crosman guns. Make sure to follow up witb lots of flushing and cleaning. A bore mop soaked in Remoil followed by lots of dry patches worked great for me.
No Bronze Brushes pass through any of my barrels,,It's Patch's with Goo Gone only.I don't know of anyone here that endorses the use of any type of brush in an AG barrel,but it's your barrel, so it's your choice of what cleaning technique you use, personally I wouldn't. JMHO