Tuning fx impact 500mm .25 tuning

[twalt12]

This is my first attempt at tuning with my new FX Impact MK2 500mm in .25 cal

I have watched hours of videos and went through 4 tins (350) of JSB 25.39 exact pellets but think I have finally found the sweet spot. It was not that hard I just had not idea what I was doing or how much hammer spring I should have be using. When I received the rifle it was 90psi on the reg and HS was totally backed all the way out. shooting at 720FPS

39 shot string

Min FPS - 865

Max FPS - 886

Ext Spread - 21

Standard Dev - 3.7

Reg is at 120PSI / Hammer Spring I will give you a number when my new calipers come in, front valve at the 3rd line(ish)



Let me know what setting you have had success with your mk2 compact in .25. I know they are all going to be different but it will atleast give you a starting point for tuning a new pellet

 

[2L8]

Congrats on your new Impact. Excellent start to your tune. JSB 25.39 work very well in the 865 to mid 900's. I would suggest at this point you put it on paper and see what the tune can deliver. Numbers are one thing and paper is another. Another thing, listen to you gun.

Have fun and keep us posted.

 

[jcote258]

39 shots that pretty good, I think! I have the MKII PP 25 cal with a 500mm barrel as well, and before I stripped it down to put in the slug power kit, it was slinging kings at 950 before the dual transfer port mod. I have to say this Impact is my winter project, so I won't be providing any accuracy notes till this spring, but I can get back to you with tunning numbers once I have the rifle put back together. To get the Kings at 950, the reg set at 135 bar and valve at line 3 with the hammer spring pretty close to maxed out, which was probably not necessary, and I noticed it was using a bunch of air. I sent many parts off to Cerekote and broke the front end down, which is currently waiting for my slug kit and 600mm barrel build using parts from FX, Pyramyd, and 910 Airguns. Once I get my slug kit installed, I'll be working on a performance formula, not all-out power, but walk that fine line between efficiency and power. While my particular setup might slightly differ from yours, it still might be a value add for you as I will be tuning the 500mm for pellets using both Kings and Hades, and my 600mm will be my slug liner.