Feeding issues, new hop-up & bucking

I recently installed a Mad Bull Ultimate Hop-up unit into my M16, as well as a tight bore barrel. Since then, I've been having feeding issues. On semi-auto with the hop all the way off, the rifle will only fire about every other round, occasionally firing a few in a row, or none in a row. In full- auto, it is much more sporadic. Even turning the rifle upside down or applying pressure to the rounds in the feed tube with a rod doesn't seem to help. I've disassemble and reassembled the hop-up unit already, and I know it's assembled correctly, so WTF? I've heard that a new bucking takes time to break in, but does it ever cause the gun to misfeed/ jam? Could it be my tappet plate/ air nozzel? Crappy air pressure?

not good:

good:

when you drop a bb in the feed tube while holding the gun upside down, does it shoot fine or doesn't drop in all the way while firing? you should not need any additional pressure to pushing into the feed tube. if you do, that means either the nozzle or bucking is blocking it. during gearbox cycling, the nozzle should retract all the way to allow the bb to just drop in. you can shoot it several times to see if the nozzle completely clears the feeding tube. you can also see (with a flash light) if the bucking is blocking the feeding tube.

Nope bucking is in right - like I said, the unit is assembled correctly. It doesn't fire properly at any angle, even upside down. When I observed the BBs in the chamber, it seemed that the BB was going in all the way, but just wasn't shooting out the barrel.

then you need to check nozzle to hopup bucking air seal... put a small piece of tissue in the feed tube and plug the end of the barrel. shoot. if the tissue blows out easily, then it's leaking badly enough to prevent the bb from clearing the hopup chamber. usually, leakage is random. sometimes you can get a bb to shoot out. also, is there a hopup spring that pushes it towards the gearbox? that also affects nozzle to hopup sealing.

Yep, there's a spring, as well as an o-ring that goes into the front of the gearbox next to the cylinder head, creating an even tighter seal. Also, important to note - sometimes, especially on the first few shots, the bbs just roll out of the barrel. Sorry for not saying that earlier.

I just did the test, and the tissue came out easily every time. What do I have to do? Should I disassemble my gearbox again, apply oil, cry in the corner?

if you don't mind opening up your gearbox. you can sand the face of the tappet plate (connects to the nozzle). if you thin it down, it will extend the nozzle further into the hopup.

since you didn't mention upgrading anything in the gearbox, i don't think you will have any timing issues that causes bb's to roll out. whenever you do get a bb to shot out, does it curve upwards or drops to the ground within 50 feet?

Oh - I didn't really think that the gearbox would make a difference. I did a bit of gearbox work recently, I replaced the nozzle, spring, gears, and cylinder head, piston, and piston head. Now that I think about it, the cylinder head had a sorbo pad on it that I never did anything about. I noticed I had two extra teeth on my sector gear that didn't make contact with the teeth on piston. I ended up just reassembling the gearbox with the sector gear's first tooth touching the first tooth on the piston. Would rotating the the sector gear so that the sector gear's second tooth contacted the first tooth on the piston have any positive effects? Is my problem an AoE problem and not an air seal problem?

sector gear position only needs to clear the piston and tappet plate. it is self adjusting during the first shot. what you need to do is measure the new nozzle with the old or manually press the hopup against the assembled gearbox. you should be able to feel some nozzle tension with the hopup. if you don't, then it will leak. sanding down the front tappet plate extends the nozzle. also check for tappet plate binding. if the sector gear is shimmed to high, it will bind with the tappet plate fin and cause airseal timing issues (nozzle not closing with hopup in time when piston is ending it's compression stroke).