Tuning FX Impact Mk2 tuning advice

[Tnp]

So I've watched a few videos on tuning and I'm still a little lost in regards to where my hammer and valve needs to be. The trend I've noticed is that everyone has they power wheel on max, valve to the 4th line and the regulator lowered while working it up to the desired fps. I've noticed some tuners like to get their fps around 15-20fps above their desired fps and use the valve knob to bring it down to where it needs to be for the purpose of efficiency. There's so much info and I have no idea where to start. 

So, my goal is to get my Fx Impact M2k in.25 shooting 25.39g pellets at 970fps with the power wheel on max. What approach should I take?

My specs-

-600mm STX liner in .25

-Slug kit installed with probe but....with the stock spring which has no rubber ball.

Ernest Rowe Dual transfer port flipped to the low power side that has been bored open

I set my tuning area up and ran some numbers yesterday and this is what I got. Am I fairly close to where I need to be?

 

[douger]

why do you wanna shoot those that fast id shoot for 895 or so 910 max best accuracy may even be slower try red at 130 valve at 4 lines hammer spring dont have to be maxed out should have plennty of play left just my opinion gun will be very efficiant also should get 75 plus shots 

 

[Tnp]

I'll be shooting the 25.39g slower by using the power wheel but wanted to tune for higher velocity for when my heavy liner and 26g slug comes in. 

 

[gbikerman]

Here are a couple of tunes I use in My Impact MKII 700MM Superior liner that work well for me. My gun has stock Power Plenum, probe and valving In my experience you will have a hard time using the same tune for pellets and slugs unless your projectile weights are similar. I have had success with pellets and FX Hybrids on the same tune (hybrids shoot 20fps slower in my gun). I also like to have my desired speed correlate with PW setting 3-5. This way I can adjust for variances throughout the day while I am shooting. It is not uncommon for a 20/30 FPS shift going from a cold morning to a warm afternoon.

Projectile JSB/FX 25.39 .25 caliber, Ambient temp. 75

Reg- 90 Bar

Valve Adj.-.40

Hammer -.725 on max setting

Max speed 930fps, speed on PW setting 3- 900fps 

With this setting I am able to shool 5 full magazines between fills on a 480 bottle in warm weather.



Projectile JSB KO 33.49 .25 caliber, Ambient temp. 75

Reg- 142 Bar

Valve Adj.-.390

Hammer -.567 on max setting

Max speed 970fps, speed on PW setting 5-960 fps 

With this setting I am able to shool 3 full magazines between fills on a 480 bottle in warm weather.



Hope this helps

 

[Tnp]

Here are a couple of tunes I use in My Impact MKII 700MM Superior liner that work well for me. My gun has stock Power Plenum, probe and valving In my experience you will have a hard time using the same tune for pellets and slugs unless your projectile weights are similar. I have had success with pellets and FX Hybrids on the same tune (hybrids shoot 20fps slower in my gun). I also like to have my desired speed correlate with PW setting 3-5. This way I can adjust for variances throughout the day while I am shooting. It is not uncommon for a 20/30 FPS shift going from a cold morning to a warm afternoon.

Projectile JSB/FX 25.39 .25 caliber, Ambient temp. 75

Reg- 90 Bar

Valve Adj.-.40

Hammer -.725 on max setting

Max speed 930fps, speed on PW setting 3- 900fps 

With this setting I am able to shool 5 full magazines between fills on a 480 bottle in warm weather.



Projectile JSB KO 33.49 .25 caliber, Ambient temp. 75

Reg- 142 Bar

Valve Adj.-.390

Hammer -.567 on max setting

Max speed 970fps, speed on PW setting 5-960 fps 

With this setting I am able to shool 3 full magazines between fills on a 480 bottle in warm weather.



Hope this helps

Thanks man. I'll start doing some tinkering tonight!

 

[Dmitch48]

Can anyone verify or confirm this..........

Well Derrick the fact that you put one of the new 720cc Power Plenums on the gun is a problem. The 720 Plenum is not really compatable with your MKII...it will fit on your gun but it will not allow your rifle to achieve anywhere close to the power that the original Power Plenum would have. So if you sent your rifle to FX to have them put that on for you, then my advice is to call them and cancel that. I will not even bother trying to tune your gun for you with that 720 Plenum on there. 

Unfortunately there are a lot of other guys like you that want to accessorize their rifles and the latest gimmick is to put a 720 Plenum on the gun thinking it will give your rifle more power, but actually just the opposite is true... it really prevents your valve from opening and you end up getting way less power. So whether you have me do any work on your gun or not I recommend you get that 720 off and put the original one back on...if you do let me know and I'll give your gun the kind of power you want.

 

[Deadshot.25]

So Dmitch48,

Why is this? I have installed the 720 plenum on my MK2 pp .22 700mm. I have slug power kit installed with just 1 spacer/hammer weight. I have my original valve spring instead of light spring. I do have a pin probe and dual transfer port. Anyways I have never heard what you are stating that you won't get the power from 720 pp on an MK2. I have no prob getting any slug up to 34 grain over 1000fps. With 720 pp I don't have to run nearly as high of reg pressure as stock pp. I'm just curious as to your findings that it won't open valve enough 

 

[Airgunmann]

Sounds like a bunch of Bs to me about the 720 not working on the mk2 bigger plenum equals less reg pressure 

 

[Dmitch48]

Ok, I copy and pasted a message that was sent to me be a tuner and so I was asking yall if this had any validation to it. I have since sent my gun to FX USA (Neuman) and it was installed. IT it will shoot 81 grain pellets at 960fps at 160 foot pounds....or something like that. In short, the 72mm plenum works and works well.

 

[Airgunmann]

Ok, I copy and pasted a message that was sent to me be a tuner and so I was asking yall if this had any validation to it. I have since sent my gun to FX USA (Neuman) and it was installed. IT it will shoot 81 grain pellets at 960fps at 160 foot pounds....or something like that. In short, the 72mm plenum works and works well.

Good to know I have one on order for my mk2 but still waiting for it

 

[Dmitch48]

Ok cool. The only problem I have with my MK2 .357 is it's barrel, it won't shoot slugs. I tried the 93 grain and the 79 grain NSAs but to no avail. However, the 81 grain pellets is on point. Down range energy is not there but bullseye at 50 yards. Man, I got a carbon fiber collar on it to help stiffen the barrel, the 72mm plenum and a harmonics tuner on it and it still won't shoot slugs accurately. I need that .357 slug liner no if and or buts about it. 

 

[Dmitch48]

Here she is. 81 grains at 960 FPS.

 

[Airgunmann]

My guess is twist rate isn't fast enough 

 

[Dmitch48]

Your guess is correct. I think for it to shoot slugs a 16 or 18 twist rate is needed. How could FX put out a .357 and not think we'd want to shoot slugs. I don't get that bru.