ZCI Aluminum M4 Outer Barrel for M4 / M16 AEG Rifles
(Length: 10.5")

"They measured it end to end not to where the receiver meets just be aware
that doesn't mean that they do stick out of it
good product

"Just buy some locktite since it's a two part barrel.

"Gun: Matrix/S&T (Rebranded S&T) M4 Stubby in Dark Earth

The outer barrel fits fine in the gun, however there are a few minor details to be aware of if you own the same gun (and just in general).

1. The stock inner barrel for the listed gun is approximately half an inch longer than the end of the threads on this barrel. This is not an issue for me since I intend to always use a tracer unit and it seems to not mind the slight overage.

2. The stock barrel/amplifier setup (the amplifier is glued on and would require more work than the cost of the barrel for me to remove) has an internal spring pressing the inner barrel/hop assembly against the nozzle. There is a pocket in the stock barrel and the spring fits in there a bit deeper than it does in the ZCI barrel... so I just removed it entirely. The tiny spring that usually provides pressure seems to be doing the job well enough to keep the gun accurate out to ranges that are not justified by the stubby barrel. TLDR - you will be losing the larger inner barrel spring but it shouldn't matter much.

Overall the barrel is well made and feels quality. Fit and finish are good and aside from the minor issues that, honestly, are more my own lack of using a ruler (i could have just measured all this stuff precisely but... eh).

I should have purchased 6" or more. The Acetech Lighter BT fits on the end of this and the knurled ring that holds the thread adapter in place sits just ahead of the start of the forward grip tube section thing (which has a name that I am too lazy to remember or look up... you know... the place where all your rails are where you put your pointless flashlight I use to locate your position).

Buy one. Use a ruler. Don't be me.