Applicability
This modification is applicable to all the Daisy 880 style guns that use a pinned abutment washer and the 880 style piston assembly. Models that fit that description are the 880, 822, 901, and possibly others.
What this modification is
This modification replaces the factory piston head and abutment pin. The piston head is replaced with a piston head from a Daisy/Winchester model 1977. The abutment pin is replaced with a piece of oil hardened drill rod. I have also tried 4140 dowel pins that worked very well also.
How this modification works
This modification increases the compression by replacing the stock piston with a piston that creates a higher amount of compression with each pump. That means this mod will increase performance for each pump count. The 1977 piston is taller than the factory piston so the compression tube must be notched by the difference so that air can renter the tube at the top of the piston stroke. I have created models for tools to make the notch. The tool sets the depth of cut and protects the inside of the tube from being scratched while cutting the air slot. I also created a tool to be used with an 8" C-clamp to disassemble and assemble the piston assembly. The video below shows how to make/modify the parts for this modification.
After creating/modifying the components for this modification they can be assembled into the air gun just as the factory components. The following video demonstrates the installation and testing of the modification.
I have found a potential issue with the early pinned abutment valvebodies.
It seams they were manufactured with a different alloy and have thinner side walls around the abutment pin hole. I experienced a failure on a 2003 model 822 after 750 shots. For valvebodies made prior to 2015 it maybe safer to limit over pumping to 12 to 15 pumps.
I hope this information is helpful to some of you. Please feel free to contact me with any questions or if you would like to purchase a PBL power mod kit. Keep shooting those Daisy air rifles!