JPK

Congrats. I have a Thys in .577 and its a very nice rifle. I also had a 470 but it was just a bit too light so I sold it. A mistake I have since regreted.

JJ did his apprenticeship with Thys and Marcel was the Head Instructor at the Liege Gun School. JJ may have worked on that very rifle.

You will get better loads by handloading unless you get really lucky. I would guess the gun would have been regulated with Browning Ammo as that is what they usually used until Federal got to Belgium.

Why not give them a call and ask? Ask to speak to Eric Thys.