I for one am a fan of BE, but an even more pump enthusiast. I've been taking a look at a lot of home made speed feeds and another option than using a card (cause it looks like you sorta plugged your peepee into the hole...are flexible pieces of plastic, or even just zip ties. Drill like 4 sections at the end of our feed tube and clip each tie so that you have the head still sticking out and use those as "fins" inside your tube. It's probably just as effective and a little more cleaner.
Don't forget to polish that barrel (you said internals, not barrel
). And lastly, to augment some of that sound, stuff some newpaper or something into the grip.
Lastly for bonus bamf points:
Most BE guns end up being formed into something else. I have yet to see a stormtrooper rifle...and so far your's is the closest to becoming it.