Fighting Bro 3.0S Gearbox installation

I got a couple FB3.0S gearboxes to try out, one specifically to replace the stock box in a LDTHK416. I’m having some issues with the installation.
The box is now fitted with the LDT’s original cylinder, FB double-seal cylinder head and FB sealed nozzle. The box performs well in itself however I can’t seem to get a decent seal between barrel and nozzle. This is with using the Tee piece which was included with the gearbox.
The LDT box and Tee mate up with locators on the side of the Tee and the face of the gearbox; the FB Tee is designed to nest inside the the front face of the gearbox, however it is a relatively loose fit, not nice and neat like that in the J9 for example.
When the lot is installed, the output from the barrel is very weak and I suspect is due to a poor seal between the nozzle and barrel. I was able to measure a gentle lob of 180-200fps with a M100 spring.

My next steps to try are; stronger tappet return spring, check nozzle fitment in the tee, check for tappet plate obstructions.

Has anyone else experienced a similar issue or can suggest a solve?

This is far from my first blaster modification but this has got me frustrated haha.

Cheers
Stax

Compare the lengths of your let nozzle and the FB one

Every mm counts as does the contact profile of the tip

goto Bunnings and get a packet of rubber grommets for a couple of $. they fit perfectly in the rebate of the fb t. did it on a metal box and have gone through 55k plus of gels no problems.
here is photo i posted on another thread.

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Are you using the FB t piece or the LDT one? Sorry - you may have said but I can be a little slow …

The FB one in my metal box. That grommet seems to work exceptionally well.
grommet won’t work with the LDT one because of the grooves.

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The new nozzle is identical in length and profile compared to the stock nozzle.
I’ll try the grommet idea, see how I go with that. Thanks!

Can’t remember what nozzle i slid onto the metal box. It was either a Kublai or metal LDT. Same any way i think. Needed to be one of those so it fitted on the head.