Skara

The only brushless motors that come with unidirectional bearings (effectively eliminating the need for a mechanical ARL) are the Solink Advanced and V5 motors (the latter is also known as G5 under Gate's branding). Unless using the aforementioned motors it's utter bollocks to remove the ARL, so is a mechanical decocking feature like the one found on ICS guns because all these do is damage the tappet plate. It's much better (and safer for the gun's internals) to have an electronic decocking feature where the gun fires one shot with maximum AB to stop the piston fully forward.

Doable, but I found that past a certain threshold (say 30 rps) it's much more convenient to build a DSG instead. I managed, by mistake, 36/37 RPS on a single sector gear running off 12:1s and 36k warhead but I had to shortstroke the sector by 4 teeth to achieve proper timing.. You will need a very good tappet plate and spring because the poor thing will be the most stressed component as it has to reciprocate at ludicrous speeds almost 40 times a second.

I kinda like the short fixed stock, I wish I had a tan/fde one to match but heh, 'tis just a test.

It's not much about the hop rubber but rather the hop unit. If I'm not mistaken G&G rotary hop units have a clicking retainer that helps with.....well....retaining the hop up adjustment. One option is to try a hop unit that doesn't have said clicking retainer so you can fine tune the adjustment, ZCI plastics are cheap enough to give them a try. Another option is to shave a tiny bit of material off the tensioner, so that when you click it in "too much" setting, it'll hop slightly less and give you the adjustment you want... it's a bit trial and error with this one.

I suggest to stick to the AR platform.. I know they're boring and it'd be just another M4 variant in an ocean of M4 variants, but the fact it's so widespread means that there are many, many parts to pick from and the gun itself can be customized both in performance and looks/ergonomics, something that unfortunately is not always possible with other less common platforms (MP5/P90). Specna C-10 is also a good alternative to the Evolution mentioned above, just make sure you don't buy the PDW stock version, those stocks are unnecessarily heavy and offer very little battery space (you can buy extended tubes but it defies the whole concept of the pdw stock while adding even more weight). You can worry about the internals later, when you have acquired enough experience to understand what you want from your AEG. Please keep in mind that while they provide a decent base to build your dream gun on, out of the box performance will not be great. This is true for pretty much every AEG.

W-⚓-🔫

You can change the barrel and handguard on any M4 to the desired length, but you're just starting out so you're better off with an off the shelf short gun. Go for polymer receivers too, they save a lot of weight and cost. Evolution is decent, on par with Specna and Dboys (their polymer body series all come from the same factory, so pick whatever you like). I would personally stay away from the 9mm platform unless you REALLY like the looks, magazines tend to be kind of bad and they're not always cross compatible between brands, whereas regular M4 mags are essentially universal, plus you have plenty of options depending on budget. On the technical side, barrel length doesn't do much in terms of range/accuracy so I wouldn't think too much about it (all my V2 based guns have barrels 155/185mm long).

The declared values are nominal, without any load applied. The actual RPM under load depends on a lot of factors, spring rating, gear ratio, shimming, ETU, wire gauge, battery voltage, battery current and so on. Generally it's impossible to achieve 100% efficiency to the declared value unless said value is not true. For example my 36k warheads are 25k nominal on 7.4v but the actual RPM under load is closer to 20k rpm. Most ETUs control the rate of fire by sending semi auto impulses at different frequencies which, as Lozart mentioned, doesn't affect the actual cycle time of the motor/gearbox. For example, if your gun cycles in 25 milliseconds (netting a FA rof of 40 RPS), full auto at 50% won't make the gun cycle in 50 milliseconds, but rather cut the cycles in half (so 25 millisecond cycle, 25 millisecond delay, 25 millisecond cycle and so on to achieve a "finished" rate of fire of 20 RPS).

Well it's not that easy to build a performing AEG out of the blue without any teching experience. First of all you need to set a goal (rps, energy and such), then you need to understand how things work inside the gearbox before even looking at a website to buy things. Plenty of guides around the internet, watch them and learn the theory behind teching. Only after you've done all of this, you can look at your gun and check if you can actually achieve your goal with that or if you are better off buying a second gun.

39k brushless motor + 13:1 gears, in that long of a barrel... Have fun destroying all your internals

Skirmshop sells halo/nano screen, I'd use Theyma only if bulk buying one specific tone/material.

That indicates that either the nozzle is too long or the hop rubber lips are. Is the hop rubber stock? Borderline impossible, there is a guide on the right side of the gearbox the plate runs onto, it keeps the plate from bending and doing what you described. In any case the plate would have to bend so much it would snap in half regardless.

That nozzle bouncing back and forth doesn't look normal, but it could be me. If you turn the gun upside down and place a bb on the feed tube (without pushing it down) and fire a shot, does it drop in the right position?

Is the gun ICS oem or you just happen to have a ICS plate? Judging by the length of the stock nozzle I guess it's the former. Are you using a delayer chip of any kind? Tappet plates do wear out with time, the front of the fin (the only part that touches the sector gear, at least in theory) gets hammered with each cycle and some manufacturers insist on making these out of cheese (ICS is one of them), so it could be worn out to the point it doesn't fully retract anymore which in turn prevents it from feeding. All of this happens more quickly with higher ROF guns. Get some pictures so we all can have a better understanding of what's going on.

For high caps buy Lonex Flash mags. Best high capacity M4 magazine out there, fits and feeds on most M4s even at 30+ RPS, pulling the cord makes more noise than winding the wheel but you only need to do it once, maybe twice, for the whole 360 rounds. Midcaps are okay if you don't use full auto (or can't due to site rules) but generally they end up being more expensive, especially when you look into quality mags and a proper Odin speedloader. I almost exclusively run the aforementioned Lonex high caps, have yet to hear the infamous battle rattle unless I'm vigorously shaking the gun or I'm tumbling down a hill like a sack of shit (thankfully the latter hasn't happened.....yet), also if I'm sprinting somewhere it means that stealth has already gone to hell and the tiny bit of extra noise isn't going to make things any worse. But I do understand the "realism" aspect of changing magazines more often. Also keep in mind that 200+ round midcaps require a REALLY good speedloader (genuine Odin, or one of those newer electric ones) and that once you get past the 150rnd mark you start experiencing heavy midcap syndrome.