Fx Impact MK2 with Power Plenum in .25

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drbytes

drbytes

Member
Dec 24, 2016
44
2
none, Belgium
Hi



I'd like to shoot the JSB Kings (25.4 gr) with this gun.

Is there anybody that can tell me what the reg has to be set at to get these guys to fly at 910 FPS? I have it around 90 bar and I get 916 fps to 906 fps, hammer spring has been tightened with wheel on max. Valve is on 3 lines.

Just looking for experiences of other people, what settings are used, etc.

Is 910 fps even a good idea? I'm looking for accuracy



For that matter, maybe I need the heavier pellet (34gr) for better results at a lower speed?





Thanks
 
Well.. I HAD it set to 910 ish and I went out this afternoon to zero my scope and do all the ranging, (MTC Viper Pro) but when I compared what I had recorded vs what chairgun gave me, it just didn't line up. Shot a couple rounds over the chrony and it was at 880/860. Hmm.

I dont know why that happend, .. did the hamer spring screw loosen? No clue. I've done some re-tuning and I have it on 935 atm but it's nigh on midnight here so I'll pick it up tomorrow. Walked the reg back up to 100 bar. Will see tomorrow.. Only second day with the impact mk2 :)
 
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I am no pro at tuning but I believe there is a game to it. I will agree with Bob_O that it’s a good idea to study Ernest R. 
video on master class tuning until you learn how all the components on the air system work together. It was a great help to me learning about harmonic tuning Bob does a few good videos on it as well. Either way don’t get frustrated and have fun doing it there’s nothing like knowing the limited of your equipment.
 
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No I did not max out the hammer spring.

What I did was lower the reg to 70-80 bar and step it up in sync with turns to the hammer spring, valve always wide open until the very last when I got around 910. I've been using the 25 grain pellet. I ended up around 90 bar and 906 - 916. Took it out on my range one hour later and wasted half of the afternoon shooting it underpowered :/

I should've at least checked again, dumb move. It makes sense that springs and valves will have to settle.
I hope it's not related to my cheap as dirt chrony; it's an Element E1000. They get good reviews and back then I didn't realize a chrony is just as important as the gun.. anyways, it should be an ok chrony.

Today is the next day, I'm going to do this again but I'm out of 25gr, I'll have to do it with the remaining 34 grs.

Are the 34gr better accuracy wise than the 25gr? Bucking wind etc?

EDIT

Ok, so it seems I'm going to get better results with the mk2 heavy, I'll order some extra tins and play with the two remaining tins I have here.

BC of these heavy mk2 seems to be 0.040 -> 0.043 , that's pretty good.
 
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Hi drbytes

I installed my power plenum today.

.25 cal 600 mm barrel Impact Mk 2.

So I started with 120 bar on the reg and the valve adjuster at 4 lines and got 879 fps

So tried an experiment and started to wind the knob back towards the o'ring.

Speed increased 879 to 884 to 905 to 923 with the knob right back towards the o'ring.

Prior to the power plenum the 25.39 JSB were shooting around that speed 923 fps.

So started tuning from this point.

I want to shoot the Mark 2 heavies 33.95 with the power plenum. I used JSB 24.39 previously.

So I was using up my 24.39 pellets.

Hammer wheel 17.48 mm and the Valve adjuster at 14.42 mm

With reg at 120 bar JSB 25.39

The measurements are for the power wheel I did not touch the valve adjuster.

17.14 mm -937 fps

16.91 mm - 944 fps

16.71 mm - 958 fps

16.38 mm - 967 fps

16.11 mm - 972 fps

15.65 mm - 981 fps

15.19 mm - 981 fps tried a 33.95 and got 888 fps

Upped the reg to 130 bar

15.19 mm - 997 fps the 33.95 - 900 fps

15.16 mm - 1002 fps

14.86 mm - 1002 fps the 33.95 - 907 fps

Upped the reg to 140 bar

14.86 mm - 1014 fps the 33.95 - 914 fps

14.68 mm - 1016 fps the 33.95 - 920 fps

Took 129 shots to get here.

I stopped here and will see how the accuracy and shot count go.

Regards

Deafdog




 
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Thx for the info.

So here's the result of an afternoon tinkering with the impact on the border of France and Belgium. We had exceptional good weather with almost no wind.
I tuned the thing to 860 with the heavy. Left it for an hour, came back and fired 5 pellets without measuring. Fired 10 more, avg was 860. Good stuff.

Reg on 100 bar, VS on 2-3, hammer spring.. dunno, have calipers, but did not measure.

Went out and measured out 0->60 meters and dailed the mtc viper. I have adjustable fx no limits but results were (its completely arbitrary though)

60m: 4, 50m: 0.5, 40m:29.1, 30m:28.1, 20m:29.5, 10m:9. (1/4 MOA)


 
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