Gearbox & troubleshooting

[Crimsonknight3]

Okay, to put it simply, due to money/time constraints I had to modify my src plastic gearbox to fit in a aps asr shell. The only thing I really had to modify was to sand down some of the plastic reinforcement around the screw for the stock to make it fit into the lower receiver. I also switched out the src stock cylinder/cylinder head/nozzle (the stock version the cylinder was plastic and the cylinder/cylinder head were all one piece. The flat plate that the air nozzle connects to though I had to use the stock all-in-one-piece air nozzle as the flat plate/metal nozzle wouldn't fit into the plastic gearbox. 

 

Now my question. I can't look at the gun today so while I can't work on it I was wondering what troubleshooting steps I should take. Essentially when I was test firing the gun, I used a low cap mag and filled it with about 30 or so bb's. When test firing the gun would randomly stop feeding and the only way to get it to start again was to remove/replace the mag. Now when I dismantle the gun again, what should I be looking to check? The hop up in the gun is just a craptastic plastic one that came already on the steel barrel because I was too lazy to replace it with the 1/2 plastic 1/2 alloy one I have. The magazine retaining clip is good and tight. I have yet lubed the piston or air nozzle but gears are shimmed and greased. The main reason I hadn't done everything before reassembly was because I was at my brothers and soldering/modifying the year box to fit and didn't have a whole lot of time. Good news is my mosfet works like a charm. Downside is I have no chrono and the gun seems to be a lot more underpowered compared to when the plastic gearbox was in a plastic gun with a longer barrel.

So question 2 is will a shorter barrel generally make a large difference on fps? Or is it a negligible difference? Also if anyone reading this is in/near high wycombe and owns a chronograph, can i come use it? Lol i have the spring from my plastic gun which, with the longer barrel was bang on 330fps but I also have a totally unknown spring that I wouldn't mind testing if the shorter barrel turns out being my lower power issue

 

 

As usual sorry for long messages and thank you for all your guys help