Main problem is that dropper assembly use brass weight to seat a bullet into case. Sometimes this force is not big enough to properly seat a bullet into case. When I was using Mr. Bullet feeder without MARK-7 this was not so annoying. I got dropped bullet about every 50 rounds so not a big deal. But when I purchased MARK-7 this problem made me crazy and I got a lot of jams and spilled powder. Our solution to a problem is to increase bullet seating force with spring rather than weight. So upgrade product is born - Dropper Assembly Solution for Mr. Bulletfeeder.
Upgrade kit contains: Custom spring holder tension coil spring and hand knob screw to attach spring and no tool disassembly.
I got running my MARK-7 on XL650 about 5K rounds without bullet drop.