Hi

What is your regulator pressure and pellet speed?

Indeed the JSB Heavy won't group.
I shall buy some 18Grain H&N
Use the JTS now and they don't do it to bad, but it can improve.

Gelukkig Nieuwjaar by the way

Here some groups with a HW77K Special Edition. 22 at 30 Yards, 10 shots each.
20240101_193718.jpg