Gimmick

I did a basic mod on my NF: AR removal, e-taped plunger, 9/16" brass barrel (no couplers or anything fancy), sealed the plunger tube with hot glue, some minor internal reinforcement and a Crossfire spring addition. The problem, though, is that this thing now shoots ranges of as low as 15-20 feet. Something must have gone terribly wrong, but for the life of me, I can't figure out what it is.

At first I thought the Crossfire spring might've been increasing friction too much and reduced the blaster's range instead of increasing it. I removed that, and then the blaster shot 5 feet. My best guess at this point is that the problem lies in the e-taped plunger (too much e-tape = too much friction = lower range?) or bad lube. Any pointers?

Gun internals:


Plunger (minus the Crossfire spring):

I need some pointers on a comparison between a Fury Fire and a DTB? i.e. stock range, modding potential, reliability, etc. Buying both and testing them for myself is not an option since they both cost about 200 bucks local currency for a set of two. All I can tell on my own is that the Fury Fire is better because of its pump-action cocking, but the DTB has a better plunger (not inverse).

I tried Dragontheuthis' Maverick straw mod on my Mav, but now it's only getting ~5-10ft range. I probably messed up badly somewhere, so does anyone have any pointers?

FYI:
- I straw-modded the plunger tube as well, like in Dragon's write-up, but after the gun failed to shoot, I reversed the mod. Didn't help, though.
- I used hot glue as a substitute for spray foam (Is that bad?)
- Here's how the base of the barrel assembly looks like right now (with one half of those AR things on and the other half off):


Everything else in the gun is stock, except for a half-barrel mod. Sorry for the terrible picture quality, the only camera I have at my disposal is the one in my phone. Also, I am aware that some of those straws are off-centre, but the gun does not fire even from the nicely centred ones.