Originally Posted by Skypilot
That makes a big difference & makes a conversion of a US FAC model to 12 FPE somewhat more problematic.
Actually it doesn't.
3.2mm with the factory stroke length and piston weight is pretty optimum for 12Ft.lbs, the 2.6mm is a bit on the small side for 12ft.lbs leading to a bouncier firing cycle.
On my UK version I have opened the port to 3.2mm and it shoots really nice.
On a 23J version just change to a 16J spring.
Have a read of this for some more info: http://www.shooting-the-breeze.com/f...ad.php?t=23990
Also have a read of this thread on Airgun BBS: http://www.airgunbbs.com/showthread....hlight=Walther