FX Impact new Power Plenum and now shoots inaccurate. Need suggestions.

Jump to latest Follow Reply
Funshine

Funshine

Member
Aug 26, 2018
401
29
FL
Hi fellas: I installed a Power Plenum on my Impact X .25 700mm and now the gun has lost its accuracy. I am and have always been shooting JSB MKII's 33.95gr. The scope is sighted at 20 yards since day 1. I have not changed anything and the scope was reinstalled at the exact position etc. I did not remove the pellet liner or anything like that, so the barrel is back like it always was. Pellets seem to feed fine from the original side shot magazine as well as the 16 round FX original ones.

Its tuned to approximately: 125 to 130 bars reg pressure. Hammer spring adjustment is 14.80mm at power wheel Max. and the Valve adjuster is a little below the third line. I get between 945fps to 955fps at Max. I shoot on setting 3 which gives about 845 to 865fps. The pellet goes off to the left about 6 to 8 inches at 20yds. This is the first time I have experienced this issue and am now totally confused and tired of it. I have tried removing the barrel a few times and it did not help. Its now a jumping jack pellet gun, going back and forth. Well, left/ right.

I would appreciate any help to solve this grievous problem.

regards,

stay safe.




 
I know you said the scope was reistalled in same the position but make sure the lugs are back against the stops in the pic rail and that the rings are snug/tight to the the pic rail. I've made that mistake more times than I want to admit.
Click to expand...



Thanks for your reply JCD, I thought of that, and have taken it off and remounted it twice already as I had marked the spot it was on the FX scope rail. I am using the Athlon Midas Tac, and have used the Wheeler Big Fat torque wrench to tighten the screws. I am hurting badly now.
 
Upvote 0
Sounds like pellet clipping somewhere. Try shooting without anything to quiet it.
Click to expand...


Well, I took off the Sumo and it did not show any signs of clipping. I shot a magazine without any moderator on and it did not improve. I saw some guys indexing their liners on You tube. I wonder if that might help. Only thing is, I never took out the liner or shroud so I cannot see why it changed POI so drastically. I am getting dizzy thinking of what to fix this *&^(*&.
 
Upvote 0
Hi fellas: I installed a Power Plenum on my Impact X .25 700mm and now the gun has lost its accuracy. I am and have always been shooting JSB MKII's 33.95gr. The scope is sighted at 20 yards since day 1. I have not changed anything and the scope was reinstalled at the exact position etc. I did not remove the pellet liner or anything like that, so the barrel is back like it always was. Pellets seem to feed fine from the original side shot magazine as well as the 16 round FX original ones.

Its tuned to approximately: 125 to 130 bars reg pressure. Hammer spring adjustment is 14.80mm at power wheel Max. and the Valve adjuster is a little below the third line. I get between 945fps to 955fps at Max. I shoot on setting 3 which gives about 845 to 865fps. The pellet goes off to the left about 6 to 8 inches at 20yds. This is the first time I have experienced this issue and am now totally confused and tired of it. I have tried removing the barrel a few times and it did not help. Its now a jumping jack pellet gun, going back and forth. Well, left/ right.

I would appreciate any help to solve this grievous problem.

regards,

stay safe.



Click to expand...

Funshine, This is just a guess on my part, but I think your new PP has changed your original tune dramatically.

Impact tuning instructions are available to the nth here on AGN with the tuning experts (thank you all!!!)



I am no "expert" but this seems like way to much HS tension for a starting point with a PP. Without PP, FX and Ernest Rowe both have HS set around 18mm on MAX as a set point. I would recommend a full "factory re-set" , so to speak, as a starting point, adjusting to your best new tune with your PP and 33.95's.

I have heard newly shipped PP Impact .25 setting currently are around:

  • Reg. 105bar
  • HS MAX set @18mm
  • Valve set 4bars

My 700mm PP .22 is currently set @ .716 HS MAX, @102bar for JSB 26gr slugs shooting 931fps

As we all know YMMV.



Be safe, shoot straight,

Patrick
 
Upvote 0
Patrick, without the PP, I had HS set to 17.10mm and the Reg set at 140 (as per new gauge indicating) and the valve at third mark. This gave me approx 900 to 915 at Max and I had no accuracy issues. 

With the PP, I started out with Valve at 4th line, Hammer at 17.10mm and the Reg at 100. My FPS was in the lower 800's so I raised the Reg accordingly to 130 but it was not doing much with the FPS without adjusting the HS. 

I do see that most tuners are Maxing out their HS tension so I am not sure what you meant by taking it to 18mm. Anyways, tomorrow I will try a complete change up to see if it make a difference. 

Stay safe and thanks for the suggestions.
 
Upvote 0
You must log in or register to reply here.
Top Bottom
Back
Home
Forums
Resources
Menu