I built this ammunition loading system, and I've tried it. It works only with the addition of a ball and a spring in the system, to allow the passage of a single spherical ammunition 5.5 mm. Otherwise, two or three enter and lock.
My explanation is like in the diagram. It is impossible to stack in balance two or more spherical balls (1). In (2), the balls are as they should be, but when the spring of the tube where the bbs are lodged makes force (3), the ball inside the barrel moves to the left because it can not do it the other way, and two bbs to the barrel (4).
I have added a hold so that the ball that is going to be fired, can not go to the left, and so it works correctly, firing only from a bbs.
Apparently, after the explosion, there is an intense depression inside the barrel that is what "sucks" the ball that does not have to etrar yet. The gases have mass and when they are accelerated, when leaving the tube, inertia is what causes suction. This contributes to entering two or more bbs, when only one must enter.
I leave a couple of diagrams of how it looks. I used a short-fire gun for tests, because the regulation of everything varies. This system, in my opinion, lacks the flexibility to adapt to the variations of the different shots, in terms of power. Of 20 shots, it was locked in 4, by small variations in the mixture of the hybrid. It is understandable because it is a thing done in the house with few things. The other system, which is shown in the video, being its drive independent of the combustion pressure, fits perfectly. In 50 shots none fail!
Another problem is that he mistreats the ammunition a lot. I am shooting with lead bbs and the violence of the actions that occur within the system, the lines and deforms ... The system that I am using in the video, treats them much better.
I will continue with the system I am using, I will only add the o`ring retention, and the needle to gently press the bb against the o`ring. The pneumatic actuator that drives it will be redimensioned to optimize the consumption of compressed air and will be longitudinally aligned so that it does not disturb.