What is the diameter of the transfer port on the Hatsan 125 FAC?

[Atom]

I am interested in caliber 5.5 mm or .22, and it would be good to specify other existing calibers as well...

[Toxylon]

The last time I had my full power H135 .25 cal in pieces, I probed the TP with a 3mm drill bit shank, which went in easily but nowhere near as easily as into a 4mm hole. I didn't have my 3.5mm drill bit at hand then, but I suspect that would've been really close.

I never measured my FAC Falcon Hunter .22 cal, which is technically a H125, only somewhat better made.

Online, shooters have reported 3.5 and 4.0mm as their FAC H125 TP diameters. It seems, but is far from certain, that there have been various size TP's in the big Hatsans, at least within a small range, and within the FAC parameter.

These days, I never fail to check the TP size of a torn down gun. The lack of data will come to haunt you, I've learned. 

[Atom]

The transfer port is 3.9 mm in diameter, I measured with a drill bit, I tried 4 mm but it doesn't go through the hole!