Retro Arms & FB Tpiece in HK

Hi all, first post incoming.

Currently putting a retro arms v2 together.

The plan is to put it into a hk416 using a FB tpiece & outer barrel adapter so I’m using the wells cylinder, head, nozzle & tappet plate to suit the FB tpiece.

I havent lined it all up yet but has anyone done a similar build? Im starting to get concerned the t piece wont line up with the mag properly?


Anyone able to shed some light?


This the metal or nylon HK?

It’s a nylon HK mate.

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I use a FB t piece in my SLR and have to run wells mags, mag terminal adapter and I had to trim the mag release to suit.
That’s with a Mk box, aren’t the RA shorter in the nose?
So maybe it’ll fit fine?

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I’ve done a similar build with a APS V2 box and used all the same wells internals and the FB t piece but put it into a M4 metal receiver and had no issues other than shortening down the feeder tube on the t piece so it is flush with the mag. I also used a Gen8/9/10 mag block not the well’s because all my mags are that variety.


I actually had time to do a quick dummy fit before heading to work for the week and I think it’s going to work, I’ll just have to trim the feed tube on the tpiece.

Also I think you’re right about the RA box being a bit shorter in the nose.