Yeah, that was kind of what I was thinking, but by that stage last night my meds had severely reduced the gorms/s² I had available to devote to the task :lol:
- my AKS-74U ROF is on the low side of medium currently and i've been happy with that using mid caps (although I am in the process of upgrading her to an 11.1V LiPo for initial trigger response and naturally, unless I buy a more complex MOSFET than the simple AB I have to control it, that will result in an annoyingly higher ROF) so my choice of CQB / woodland FPS is primarily about choice of spring and barrel, but you're trying to tune your beast much more finely, so yeah, swapping out spring, piston & cylinder together to up/down from 340<=>365, if keeping the ROF so high is your main aim in either case, could be the best bet. But if you think about it, assuming you get 35rps at a consistent 365, then a simpler way to get down to 340, rather than having to start from scratch, may be to swap out the barrel...
Hang on, hang on, I know, 25FPS difference in such a short barrel...? Well, you get about 30FPS by dropping a med-long barrel from 6.08 to 6.03mm and up to another 30 by dropping down to 6.01mm diameter. So yeah, if you use a 363x6.01mm TBB for woodland and swap that for something like a 300x6.05mm for CQB, then you may well have it. That also means you can use a weaker spring, which is easier for the motor to pull, thus giving a higher ROF...
Surely having one cutout will imbalance the piston at high speed and cause extra wear?
Yeah, you'd think so wouldn't you? TBH, even though you wrote "one cut-out", I assumed you meant one on each side. I can only assume that, if they even care, Element decided that this Universal Cylinder would not be chosen by techs doing high speed box builds.
I keep meaning to build an MP5 so that I can learn the V2 GB, but I'm not a gun tech per se and M4's don't suit my body and hands, so I'm not familiar with the hop units you're on about, but yeah, by the sounds of it I'd have sent the 'kin thing back! As far as I'm aware the ICS M4 hop unit has a good rep, but I can only tell you from personal experience about their AK one in comparison to the TM / clone / compatible ones - whole different creature.
It's attached by long bolts parallel to the barrel which go through the clip that locks the barrel centralised (fitting into those side grooves on barrels) so it's much more solid than the TM which uses a poxy little 'C-clip'. It's made out of a very shiny, somewhat brittle, plastic, which is kind of surprising but it's plenty strong enough for the feed tube to resist being damaged by clumsy mag changes. I can only guess that they really wanted the surface to be resistant to wear and very smooth so it doesn't add much effect of its own when the hop rubber squeezes the BB against it.
Anyway, yeah, t'other week I strolled into a conversation, as you do, without having heard what had been said as somebody shouldered his AEG to shoot a few shots at a pole about 40mm wide at maybe 22m - I raised
Phatima pretty casually, not even using the front sight pillar, just the kind of instinctive shot that you'd take at somebody who surprised you coming around a corner - ding! Hit first time. Ding, ding, ding, etc. - turns out the convo was about accuracy and how fettling guns for it isn't necessarily so easy :lol:
So that isn't me boasting, b/c I'm not a bad shot but I don't think I'm exceptional, nor do i think i'm a top drawer gun tech, but it's prelude to saying that yeah, the hop nub is crucial. The set up - standard ICS hop chamber, gucci rubber (I forget), Madbull Fish Bone Spacer (that's what they call an H-nub), Systema BS(lol) 6.05 x 225(iirc)mm (MP5 TBB = short for an AKS-74U but I got it cheap so tried it out and just haven't got around to swapping back to the one I had in her before) & Blaster 0.25g BB's. IMO it's a case of nothing in the chain is bad for accuracy, but the only thing which is good for it is the nub:
- it only just fits into the space allowed for it, so it cannot be anything but bang on central to the hop unit
and those flanges at the edges make the rubber engage with the BB equally on each side and wrapping around so it forces the BB into the centre of the hop chamber, whereas a simple cylindrical nub presses down on the centre of the BB, wherever it is in the chamber, so naturally the space needed for ease of BB feed and the tolerances that the system can be engineered to, at sensible prices, mean that the BB must be starting out on one side or the other of the chamber and as the pressure of the nub comes down central to the hop unit, there is a slight discrepancy there...
- it's difficult to explain what I mean without a diagram (I may draw one later tonight), but I hope you can imagine what I'm on about - the rubber is squashy, most nubs have some spring in them, the direction of force is off centre to a spheroid, hence it must impart more spin to the side of the BB opposite to that side of the hop chamber to which it is closest, which must be unstable since that will make the BB tend toward that side of the barrel and bounce off... from then on you'd need a supercomputer to work out what happens to the spin as the BB bounces back, forth, up, down, etc. down the barrel. The 'exit cone', iirc its name, describes the potential trajectories of a BB exiting the muzzle and the more unstable the spin, the wider it is. In an ideal world the BB would leave the hop chamber with back spin on an axis exactly perpendicular to the centre of the barrel and then pretty much only gravity and shooter movement would widen that exit cone from close to a straight line, but obviously that isn't the case... measures such as H-nubs / X-Spacers / Fish Bone Spacers, in a complex way the "biro-refill mod", and hop rubbers with a built in division such as PDI W-Hold, Falcon Dual Point, stock CYMA, all go some way towards getting closer to the ideal.
I like that stock - I mean the paint job in general is lush, but the stock makes it look like a custom weapon rather than just another (yawn) painted M4.
