Forgot to mention about possible nozzle seal leaks in the ACR.
Can always try out the old “o-rings in the t-piece” trick and see if your FPS improves dramatically from there? 
Aaaaah… that’s better.
Consistently just under 300FPS… Amazing what running the right spring will do. Full M100 
Happy with that, now to work on a barrel stabilizer and it’s done. Then what am I gonna do? 
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Go out and pew pew to your hearts content and enjoy mate! 
PS: Love the ACOG, looks exactly the same as the genuine Alloy one on my Bushmaster DMR. 
Go farming like me, plenty to do haha
Quick fettle with the acr/r.
Brass cylinder head and nozzle. Green o-ring, still on stock spring with 40cm alloy barrel got a nice 275-285 fps.
Was going to do an m90 but I didn’t have one! Thought I did, oh well, might get one on the weekend and swap it out, also might be happy enough with it as it, shoots nice and consistent now.
It’s going to get front wired at some point anyway 
I chopped a bit of 10mm thick rubber mat up into a shape that works as an outer barrel stabilzer for mine this morning. Looks rough as bags because it was an old mat and shitty rubber but proof of concept 100%.
When I make another out of sexier rubber I’ll post pics up. No disassembly required, just pushes into the front of the handguard and locks the outer nicely.
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Quick operation and put the stock spring from my JG Aug in the acr/r… pretty happy with it now.
Of course this is only temporary to see how it goings. Well it seems!
Mostly 320-330fps.
The plan, nylon j10 box will have a wire extension made to fit in the j9, along with ported cylinder to match the much shorter barrel it runs.
The mk box in the j9 is going in the acr, along with a brushless motor… and will be rewired to the front.
Will give the internals a refresh but it will be an efficiency build more than a rps/fps monster, that way it could run all day on the battery that fits in the handguard, or peq box.
Also have a metal parts kit which I will only be using some of.
Would love to find a metal outer barrel, so far only seen the long one available at x-force, and I think I want to keep it the original length.
If anyone wanted one of those Remington handguards for an ACR Ausgel have some on sale for like $40, although its the plastic one it says
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@RokSolid That’s going to be one solid ACR build.
Do you know if it’s correct that a standard V2 box will fit into the receiver of an ACR no problem? Or does it have to be Gen 9 shape at the rear? 
I’ve got a full metal CYMA box here that’s looking for a home and I can’t think of a better place right now off the top of my head than in an ACR.
@DChapo nice handguard… shame it’s not metal but that would drive the price up. . Lucky I like the Masada style handguard on an ACR. 
SIXmm have a few ACR parts, an alloy RIS handguard for Masada AEG… might fit.
They have a few steel outer barrels of different lengths too but only for GBB ACRs.
I know the standard box is a gen9, and the mk box I will be transplanting is the h92.
Before I do it I could look at seeing how the spare cyma metal shell I have fits.
I remember some years ago I go a V2 gearbox working in a gen9, cant remember details but there was a lot of little “just doesn’t fit” things about it.
Don’t know who supplied these, possibly EVIKE or some other Airsoft company.
Alloy BUSHMASTER handguard, Alloy outer barrel and gas tube, metal replica gas valve and recoil spring on the gas tube inside the handguard., t-piece is standard plastic ACR.
Looks like the brand PTS on the printing, which looks like all markings were possibly once white lettering that has been painted over in black, making it different to see.
@Friendly_Fire Definitely require the Gen9/10/MK Hybrid Gearbox due to the shape of the pistol grip/reciever.
EDIT: FOUND THEM!
EDIT: Out of stock 
Looks like Sixmm is the place to go looking.
I remember something exactly like the above, there is some clearance and alignment issues. Somebody had a go at it on the old forum and iirc got it done. Just can’t remember exactly what. Something was a pain to line up iirc.
Or read above per the Doctor 
From memory of my own mucking around, it’s mainly the shape of the rear of the gearbox in the reciever, getting the gearbox down low and forward enough to allow the trigger, motor screws and the centre pin to align through the gearbox/reciever body.
Ah bugger. Oh well, Gen 9 box it is. Cheers, Doc…
No worries…the J9 box will definitely save your sanity and pulling your hair out, not to mention the swear jar most likely shattering! 
Shame… it would have been nice if a V2 did fit…
Gen9 gearbox shells weren’t exactly the duck’s guts… okay if you keep the upgrades mild but tended to warp with high loads put on the bearings. Why I always kept Gen9 builds around the 280FPS mark.
I also got in the habit of building up around the AR post with either epoxy or CA with baking soda. Another well known Gen9 failure point.
Then again there’s always the option of a MK CNC Hybrid 92 shell. Safari Zoomer over in Maiphut’s neck of the woods is the cheapest at $220.
Yes the gen9 gearbox is one that, might as well just do seals, m90 and run 11v. Any faster motor or bigger spring always led to the box warping and ruining gears. They do run pretty well like that though.
As for the metal cyma box… it could work!
Bear in mind that the acr/r doesn’t have a rear receiver pin, so I can’t check that. But the centre pin seems to line up, as does the motor tower holes in the grip area… screw holes of course in the grip area will need to be elongated to suit the V2 standard which is different from gen9/10 slightly.
The rear of the gearbox on the cyma is a couple mm shorter than the gen9 at the spring retainer but that’s irrelevant on an acr, not screwing a buffer tube on anyway.
The only thing I seen on the lower that would be a problem is this “fin” on the receiver where the magazine wire channel protruding on the side of the gearbox, easy modification to receiver, or if you’re game gearbox as both mean little to strength.
And of course the tpiece would be fun, as the barrel adaptor doesn’t suit it, but again you could put horizontal cuts in, or maybe drill out a j9/10 tpiece and use it as a sleeve for the cyma or ldt tpiece…
Mate… compared to shoving an MP9 box into a diecast UZI capgun and making it work?
Getting that box to fit and function would be a cakewalk. Although springing for a H92 would be a lot less work. 
Thanks for the trial fit photos too, RokSolid. Much appreciated.
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No problem… Definitely easier than the uzi build!
I am now debating whether to pilfer the h92 or just shoehorn in the cyma box… so… Thank you?