APS T-Piece connection problems

Hi Guys,
I’m building this all metal rig based on a APS gear box. Finally got one of those elusive FB T-Pieces which are supposed to be the best match for this box but the extended lip on the T-Piece which is suppose to fit snug on the end of the gearbox is a bit to big.
I was thinking just opening up the whole on the box to fit the t-piece, is that the best solution?

My other question is concerning the same t-piece. What is the best mag for it. I was hoping to use gen9 type but looking at the down pipe it appears to be about 5 mil longer than my gen9 t-pieces. Am I going to need Wells mags for this t-piece. I have never actually seen a Wells mag. How is the down pipe connection?


Probably opening up the end of the aps box will work???
Honestly that aps box is a turd, that’s why it’s in my sons blaster😂.
I’ve also just got my FB t piece, I’m using a SLR receiver and Gen 9 mag. Everything lines up great so far🤞🏽.
The t piece sits nicely in side the V2 box and lines up with the gen 9 mag. So if you open up the aps box to fit the t piece it should be the same?
The wells mag is on the bottom in the picture if that helps.

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Ok, so my FB t piece gel feeding part is long as well and will have to be trimmed down otherwise both gen 9 and Wells mags won’t fit all the way in🤬.

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Thanks @Hiroshima_screamer, so what metal V2 gear box are you using? I know there are a heap out their but I just got the APS because I needed an existing mag block which I knew would work for gel balls.

Ok so you have the same problem with the down pipe. I thought maybe the Wells mags didnt have a capped end and the pipe just went freely down without having to worry about length, so that is not the case?

@LowGuido what t-piece did you use in your APS build? I didn’t see anywhere you mentioning having to open up the end of the gear box to fit the FB t-piece?

Thanks legend

Absolutely stoked to see this as I’m collecting bits to jam a retro arms split into a JJ SLR receiver

Are you using the FB barrel Adapter ?

I was looking at the FB Adapter the other day pondering if it would all line up.

I presume I won’t be using the JJ barrel or barrel adapter

Hey bud, mine is the first metal v2 box that m4a1 brought out for the wells months and months ago.
Cheap cast metal but I’ve hammered it and it’s still going strong.
Tossing up between retro arms and Mk tactical box next, think I’ll support local and get a Mk one👍🏽.

Yeah both mags fit the receiver but the FB t feeding pipe is to long for both, I’ll just shave it down

Seems to line up fine, I’m using the FB barrel adapter and not the jj one.

I did have one issue and not sure if other people have had the same problem.
When I put the metal v2 box into the slr receiver it wouldn’t close properly.
The charging handle must be designed for the priming feature on the jj gearbox and is quite thick. I had to dremel he charging handle thinner so the receiver would close.

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Hi @zeHamish my build is using a M4 metal receiver which the APS and I guess the retro arms box would fit in. I’m using the FB t-piece but not the barrel adapter as I prefer something where a screw on lug like the gen9 has with the delta ring. I don’t trust a connection which is based on a small grub screw.
This is what I’m using, a big barrel nut screws over and keeps it tight.
I will have to alter the inner barel end to fit the big square blocks on the FB t-piece.


@Hiroshima_screamer mate the @MKTacticalHobbies is by far the best dedicated after market gear box to go for. Got to love a local product which is the top of the game and designed specially for gel balls. Have you noticed the extra front travel it gives like the gen9? Most others don’t have that because they are designed for 6mil airsoft and not 8 mil gel balls.


Must say, the CNC V2 metal gearbox that MK Tactical Hobbies has looks great, but expensive !
If it would fit in my LDT HK416 ok, might consider getting one later on, but not for awhile…

mate just use a file to widen the diameter of the nozzle opening on APS box by around 1/4 mm. Go bit by bit and you’re on the money when box is closed and there is no resistance when turning the T piece. The reason you don’t want it to too snug is because of the way stress forces are transferred. Whilst you are at it, may as well radius the box as well


thank you for your kind words @Maystro :slight_smile:

@spectreman there has not been any official testing done with LDT HK416 yet but its in the queue. Keep an eye on the product page https://mkth.com.au/products/metal-v2-gearbox-casing for updates to compatible receivers list.
Feeling you about the price man but with 3 hours of machining required to produce the box we’ve lowered the price as far as we could (and then some)

I used the stock wells T piece.

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@LowGuido mate I’ve been looking for someone to connect us…
can you please message us at https://www.facebook.com/mktacticalhobbies/? Thanks

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That sounds like an endorsement opportunity. Nice bro👍

APS :point_right: SLR is a great setup but requires modifications of the box, t-piece, outer barrel adapter to work efficiently and be reliable. Using the FB tpiece is also the superior option if done correctly.

DO NOT USE ONE PIECE CYLINDERS in the APS box as they cause premature failure.

I have many customers running this configuration (not the one piece!) and with the spring that comes with the APS and a 34cm TB barrel you should have muzzle velocity of 380 FPS.
The bearings that come with the box are the best I’ve come across and if maintained correctly they exceed all expectations.
The switch supplied with the box barely handles 7.4v and melt with an 11.1v Lipo fitted.

Did I mention DON’T USE ONE PIECE CYLINDERS, they cause the box case to fail.
Stick to18:1 and the Genuine spring for best service life.


From many people I’ve seen and spoken with APS are prone to fail failure… period

i haven’t seen one in the flesh but that is what i hear also from ppl who go back to nylon boxes

i wonder if its a build fault or something really trivial that just causes failures