Fx impact MK2 power plenum lack of POWER!

[RC_Bladeworks]

I have the new .25 cal fx impact mk2 with the stock power plenum 600mm slug barrel shooting 33.5 grain nsa slugs. I can't get over 938 fps! Here is how i did the quick tune to figure this out;

I backed out the valve adjustment knob past line 4. I Maxed out the hammer spring with the Allen wrench just so that the power wheel wasn't binding. I started at 100 bar and went up in 5 bar increments (digital gauge) to 160 bar. I used the power wheel from Max to min to get a ball park fps for that reg setting. The max it hit was 938 fps?

I totally disassembled the gun and checked everything for tightness and check all the orings and everything is perfect (new gun). I can't figure it out! My goal was to get it around 950 and fine tune down from there. 

If you have any suggestions or tell me your tune for this that would be great! Thanks!

 

[jking]

You can probably get to to your target velocity by elongating and porting the brass inlet and modifying the probe. What are others getting for velocity with a 33.5gr slug? How fast is it shooting a JSB 34gr heavy at that tune?

Jking

 

[buttles]

Hi, I have the exact setup as you. I shoot the 36.2 NSAs. Maxed out like you I was getting 915. I put a v2 hammer spring in and it went up to 940. You need to bring the valve adjuster in or it's very clangy on the hammer!!

 

[spyde82]

Hi, I have the exact setup as you. I shoot the 36.2 NSAs. Maxed out like you I was getting 915. I put a v2 hammer spring in and it went up to 940. You need to bring the valve adjuster in or it's very clangy on the hammer!!

V2 spring?

 

[RC_Bladeworks]

What reg setting are you on?

 

[RC_Bladeworks]

Hi, I have the exact setup as you. I shoot the 36.2 NSAs. Maxed out like you I was getting 915. I put a v2 hammer spring in and it went up to 940. You need to bring the valve adjuster in or it's very clangy on the hammer!!

What about making a 4mm aluminum spacer instead of buying the old spring (i have a mini lathe)

 

[buttles]

Packing out the 'new' plenum spring should work. I tried it on a Brocock and it worked. You won't get the full benefit of using the v2 but worth a try.

I'm on 165 bar. I wouldn't say the power level you have is technically a 'Lack of Power' though?

 

[sonny]

Im shooting the 34s at 910-915 from 125 bar reg after backing the hammer spring tension from max to give a little play on max wheel when not cocked and turned the valve stop in showing 2 and 1/2 lines. The shot string is very consistent, with 70+ very accurate shots on a 250bar fill. If I remember correctly when I started same reg setting hammer spring maxed valve stop out 4 lines 34s shooting 945-950? It was loud and sounded harsh/snappy before I tuned it down. The tune for reg setting seems perfect right now as when it drops of the reg the poi drops with it. I have the MK2 with original S/T 600mm barrel.

 

[RC_Bladeworks]

Im shooting the 34s at 910-915 from 125 bar reg after backing the hammer spring tension from max to give a little play on max wheel when not cocked and turned the valve stop in showing 2 and 1/2 lines. The shot string is very consistent, with 70+ very accurate shots on a 250bar fill. If I remember correctly when I started same reg setting hammer spring maxed valve stop out 4 lines 34s shooting 945-950? It was loud and sounded harsh/snappy before I tuned it down. The tune for reg setting seems perfect right now as when it drops of the reg the poi drops with it. I have the MK2 with original S/T 600mm barrel.

Your shooting slugs out of a pellet liner?

 

[buttles]

You may want to check your pellet probe seating distance. I assumed from the factory it would be set correctly but no. It was at 42mm. Nearly half the port was overlapped with the Txfr port. Odd thing is it only gave me 15 more fps when set correctly! See if accuracy inproves as the slugs will be somewhat closer to the lands.