First thing to do is determine where the bb is getting jamed.
Possible problems are if you didnt install the barrel correctly, meaning if the brass tube is not properly aligned into the top receiver the mag feed lips wont properly sit this could be an issue.
Second could be the bb chamber I believe its part #122 it sits just on the tip of the inner barrel its can be frayed or torn or swelled up from too much silicon oil. I'm guessing that this us probably what is causing the jamming issue.
I would dissemble the gun again inspect this piece and determine its condition and then order that piece and possible few backups along with hopups.
Another idea your guide rod could possibly be bent check to make sure everything is snug and nothing is loose on the any part of the bolt guide rod nozzle.
Make sure that the npas is not completely turned off or on so I would try adjust it see if that makes any difference.
Other than that try some of these suggestions post your findings and you might want to check this website.
http://wem4guide.wikidot.com/troubleshooting
There is amazing information on it and has helped me greatly.
on a side note toms guide is very well done but one thing I noticed and a mistake I made myself is really how much lube to use and how to smooth it out. these guns require a minimal amount so just make sure you are not over lubing the gun something I discovered on the guide on that website.
Best of luck!