FX FX King/Panthera extreme spread and standard deviations high?

[Lewis]

Looking for some help on the King/Dynamic/Panthera format.

We have 2 guns both in 600mm. One is .25 and the other is .30.
Both have the same behavior. The shots are mostly in the same range, say 900FPS, but every 3-5 shots is low by up to 50 fps. As expected the shots that are 890 and up are all grouping well but the group is destroyed at 100 by the low power shots.

The factory regulator gauge does not show a difference from shot to shot that I can see. I have tried higher reg, and lower reg with hammer adjustment to match. Same behavior.

Any ideas?

900
905
890
860
895
895
850
902
900
855

 

[EDventure]

What are your regulator and hammer spring settings?

 

[Emu]

Problem is always there if you do not give time among shots.

Plenum needs time to be refilled at appropriate preassure.

 

[Airgunmann]

Either wait time between shots or the reg is set to high for the hammer strike and it isn't tempting the plenum and reg isn't refilling until plenum drops low enough the hammers are on the light side for the guns

 

[NAProf]

Hi,
I have been spending some time trying to get my 600mm .25 King to shoot the JSB 25.4gr pellets consistently around 900 fps. Finally found a tune which is giving me and ES of 7 and SD of 2. I have the reg pressure at 75 bar and the QTS just below 1.25. That is a low pressure and about as soft as you can hit the valve with the stock hammer weight.
When I had the .22 500mm barrel on it and was trying to get JSB 18.1 gr to fly around the same speed I ended up going with a lighter hammer weight (the 10 g weight with the 1 mm head).
Cheers,
Greg

 

[Ta-Ta Toothie]

Factory reg when new takes forever to fully refresh. After you get many, many shots through them, they do improve greatly. And from my experience, these platforms like to run near the plateau.

 

[Rizz01]

Y'all have excellent and valid responses. just figured I'd share my recent experience.
I had a VERY similar issue last week. it was as simple as water in the air tank on the gun. Cleaned it out, rebuilt the reg with some silicone grease on the o-ring to combat stiction and everything was back to normal.

 

[Lewis]

Thank you all very much for the responses.
So far I have tried:
High reg pressures with enough QTS to achieve desired speed.
High QTS with enough reg to achieve desired speed.
Medium reg with enough QTS to achieve desired speed.

Checked for water. All good.
Plenty of time between shots.
All that is left is possible break in time.

Current settings on the .30 cal:

Reg at 153 Bar
QTS at 3.1
Dial at 10

 

[humbled.ag]

I think your hammer strike is too light. This can produce inconsistensies when the plenum is full and the valve is seeing it's top pressure.


I have a .25 dynamic. It was shooring 34g pellets at 890fps. My initial tune was low power with a light strike. I experienced the same issues. I bumped the reg 20bar from 90-110. I cranked up the hamner spring(you'll have to decide). It was pushing them at 920fps and the consistent drop was gone. Sometimes a gun just doesn't like to keep tight spreads at certain speeds.

You can also try a heavier pellet. I've tuned guns for a specific round with no luck. I put a different pellet without changing anything else and the spread tightens up.

I hope this helps.

 

[Rizz01]

Dude, send it back. BRK's are awesome. You definitely got a bad one. Seems like you've tried everything humanly possible to make it work. Don't drive yourself crazy...