Samurai

It looks like it is a GBBR lower receiver with a properly, but "home" made AEG buffer tube adaptor. But that would mean some hacking around the grip too. Strange.

But you can't get a license for the PMR frequencies. In the UK there is no legal way to use this radio on PMR frequencies AFAIK.

Classic Army. Not good, but does the job. I hate dropleg things. My pistol's place is on the belt.

It's a multiplier to show how big current the battery can supply. Usually there are 2 of these: 30C / 15C or 50C / 25C, etc. The first shows how big current it can supply for a short period of time (burst rate). Meaning seconds. The second is how much it can supply continuously. So on the trigger pull you get an impulse of high current that levels to the lower value in a few seconds. The value itself is a multiplier to the capacity of the battery. So an 1000mAh battery with 20C rating gives 20x1000mA = 20A. An 1500mAh with 30C gives 45A. Normal AEGs use about 15-20A. If you have a battery that can't supply the needed current, the ROF will be lower, or the motor won't even be able to move the gears. (Because in this case the voltage drops, hence the beeping lipo guards on firing.) High torque motors, powerful springs may need currents above 100 Amps. The more powerful your setup is, the more current it needs.

Doesn't really matter. FPS is not the main factor if you can shoot people or not. In fact, it contributes far less than you think.

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Simple. Stop sweating. While operator ninja gear looks cool, you will start sweating the minute you start the game. Remove layers of clothes. Remove scarfs, remove headgear that doesn't allow sweat to evaporate. Dress so that you are a bit cold on the briefing, that way you will be just perfect while playing and fog much less. Also don't use mouth protection that directs your breath up to the goggles. Use anti-fog things as people mentioned above. Still fogging? Try shooting glasses instead of goggles. Not for heavy CQB though. Oh, and one more mean thing. Start running 1-2 times a week if you don't already so a simple game doesn't make you sweat that much.

Some 1000+ miles from here unfortunately.

Well, why not. Machine gun nest with sandbags and entrance-thing on the top of a steep slope. We built a few like that and some fire positions too like this:

That's called glue. Not that thick. Just some high speed lithium grease or similar.

Welcome. If the battery doesn't come with the gun, forget NiMh, go for LiPo. That means the battery charger also should be swapped for a lipo charger. Those are much better batteries and shouldn't cost more. Don't get 0.20g BBs. Use 0.25g.

All the above plus correct cylinder-barrel ratio and a foam filled suppressor will eliminate the piston's sound. I found that bearing instead of bushings are quieter but those should be at least 8mm. Maybe good quality bearings and 7mm for normal AEG is fine too. Thick grease on the gears. Don't forget proper motor height.

The site says it's 7.5 inch. The STTI or TM one is almost 10 inches long. It won't fit unfortunately.

Pretty f-ing good deal if you want to use those. Most of those are very special guns so selling the ones you don't need might take some time / reduced price. But even if you sell them on a low low price, still should make much more than 550.

The film is coming too:

Yeah, on my first game I didn't know about hopup so my range was very-very limited. Luckily after the game I found it and saw why I sucked - apart from being noob. But it's not just the gun. It's about knowing the game too. I've been playing for 8 years. If you give me a springer pistol and a beginner the bestest gnu, I still would have good chance of shooting him. Knowing tactics, ranges, how to shoot, being able to think with the opponent's head, luring and tricking them are things that you can pick up by playing a lot. Learning these are part of the fun.

GHK

Looks like an O ring. Pull it out. Edit: broken plastic is baaaad.

Skirmishing is for people who would like to play paintball but can't afford it. Milsim is for proper airsofters.

BB weight and quality affects the gun's accuracy the most. No hopups, precision barrels, constant fps come close to how much the gun depends on the BB. If you are after accuracy, get the good BBs. However, as you said, you need it for CQB where accuracy is not really needed, so average quality and lesser weight BBs will do fine. I'm with Esoterick: 0.25 Blasters will do fine.

Don't ask that from airsofters. The ones who took time and energy to actually measure it, will feel ashamed when they read that others' guns can reliably hit a man sized target at 100 meters. I have seen videos that stated "100 meter shot" and calculating from the BB's flight time it was only 30 - and then when I commented it on the vid, the poster said: yeah, it might have been 30. I have heard numerous claims reaching 80-100 meters and when I asked for proof they all said: ok, I will take a vid. They never returned. People usually eyeball distances and don't count the few (dozen) flyers. A fine tuned AEG shooting 350fps (with 0.20g) can hit a man quite reliably at 60m and headshot nearly every time on 40m with heavy BBs. HPA or similar kits might reach further because of the joule creep, ergo higher energy with the heavy BB used. GBBRs can have joule creep too but they are usually way less accurate than an AEG. 50m is the range for a normal, well maintained AEG, with average 0.25. 40m or less for non-maintained AEGs and/or using 0.20. Something like that.

L96 and SVD are huge. If you want a short, but awesome one, get a VSR g-spec and remove the suppressor.

Polarity reversed somewhere?

Just make sure it is not damaged before you charge it. Last week I took one of my old lipos, an 1800mah 7.4 Turnigy one, and smashed it to pieces with a metal bar. I am that scientific. It did smoke a bit after the first hit, and it smelled really bad but that was it. A friend of mine almost burned his house down charging a damaged one though. I keep mines in an empty tin can.