JSB Knockout 22 cal 25.4 gr VELOCITY

[Ninjababy]

I saw some videos on youtube people shooting knockout from 950 to 1000 fps in Impact airguns with great accuracy. 

I am having issue getting to that speed. 



I am at 145 bar in my regulator, the wheel is at MAX and I am getting only 900 or so. The valve is at line 4. 



Where I am making a mistake? please advice. 



Thanks

 

[nervoustrig]

The upper end of the spectrum you’re describing is 56fpe. That is no small feat in .22 cal. You are at almost 46fpe at the moment which is nothing to sneeze at. 

To get more, you will need some combination of the following:

1. Longer barrel
2. Larger porting
3. Larger plenum
4. Higher pressure

If you don’t know where to go from here, my suggestion would be to give a little detail on where things stand with these 4 items and these guys will get you pointed in the right direction.

 

[bubblerboy64]

I’ve found 935 to 940 the sweet spot. I suggest bumping the reg press up a little and then fine tuning the valve. The valve adjustment should be made as carefully as you can. Shoot three shot groups at about 35 yards. When you get to shooting three into one hole then move out to 100 and see if you don’t have what you are looking for. You are using the 217 diameter slugs correct ? 

 

[Ghostranger169]

You can still get good accuracy below 900 fps, but won't buck the wind as well as higher speeds:

 

[Ninjababy]

I am using 216 slugs

The barrel is 700 mm.

It has the power plenum in it 

It’s too windy today so I will try to go out to shoot soon

 

[jdanvers]

Not an FX - I've run the JSB KO's with good results out of my Taipan Veteran Long (w/700mm barrel and add-on plenum) @923fps - .216's out of that barrel.

 

[bubblerboy64]

I found that the 216 diameters just did not work at all in my impact superior liner.

 

[Ghostranger169]

.217 KOs(sorted by diameter) were waaaay more accurate than the .216 in all of my liners

 

[qball]

.217 slugs for FX! Also like other have said no need for 900fps even, slugs are stable in superior liners down to 600FPS.



to put things into perspective 25.4 grain slug at 900fps will still have 4 FPE or enough to kill most critters at 800 yards. 

 

[kd7rsrrze]

You did not indicate if you had adjusted the hammer spring. You said you were on the max setting which is where you will most likely need to be.

I have the MKll with the power plenum and with moderate hammer spring and the power wheel on MAX with the valve on about 1-1.5, yes, almost all the way in, and with a the pin probe/slug power kit and Earnest's dual hole transfer port with my regulator on 115 bar and the Superior liner, not the heavy liner - I pushing JSB monster redesigns 25.39gr at 953 fps quite easily. The FX Hybrids with the same settings are around 985 fps. I suspect this is mostly due to the dual hole transfer port and the slug power kit.

 

[Scott.Lavery]

The best money I have spent on my Impact Mk2 to get speeds up at lower regulator pressures was to install the Fx pin probe and the dual transfer port.
These after market items resulted in an increase of between 50-60fps without adjusting the hammer spring or valve.

For my rifle I have found the sweet spot for the JSB NO’s .216 is between 980-990fps