Please post Impact X/MKII Power Plenum .30 cal performance.

Good idea Chuck

I will start my test end of April here in Quebec, Canada when mother nature is out of cold winter.

I own a FX Impact MK1 with the first generation of regulator that i cannot pushed the pressure higher than 150 bars.

The FX Power Plenum kit is already installed and i have no leak.

What I have notice is when I set my barrel after the PP kit installation it was feeling tighter when i slide it in. It was harder to insert it but not dramatic.

I have been told to insert the barrel before I torque the top metal plate all the way. Job done.

I will use my .30 caliber original smooth twist barrel 600 mm and no other modification other than the original 57 mm hammer spring instead of the 53 hammer spring that come with the PP kit.

I will shoot JSB 44.75 grains and the JSB 50.15 grains in my fine tuning test.

I will get a 700 mm .30 caliber slug barrel end of May and see how it goes.

The newer MKII .30 cal with a 6.5mm valve and the 53cc fx p plenum from what I've read most are topping out at about 100 fpe without porting.

For .30 caliber the much better choice is the larger 70cc eccentric plenum produced by Michal Osyda in Poland... looks exactly like what fx is selling but with a larger internal volume, better performance and half the price. With the larger plenum a 6.35mm valve and simple porting my 700mm gen 2 sends a 66gn NSA at 948 fps at 150 bar for 132 fpe. The 50gn JSB pellet goes 1072 fps at the same pressure but I don't use them at that speed I just did it to see how fast they would go.

The larger plenum from Poland costs about $150 shipped UPS and fits MKI and MKII. Don't listen to anyone telling you the price is higher or they have exclusive import rights because it's not true. I just confirmed this with the manufacturer. If you email him give him a few days to respond because he's busy.


AT Michał Osyda


98-300 Gaszyn, ul.Źródlana 13a

Tel. 883999733



http://www.airguntuning.pl




70cc Polish plenum installed on Glem.Chally's gun.

This guy shoot D-Rig 50 grain slugs at 935 fps using the FX Power Plenum without modifications.

Regulator set at 150 bars.

700 mm slug liner.

https://youtu.be/Ze5iX84ykAk

This guy shoot D-Rig 50 grain slugs at 935 fps using the FX Power Plenum without modifications.

Regulator set at 150 bars.

700 mm slug liner.

Click to expand...

A few minutes with a rotary tool and the $150 plenum from Poland would would have him shooting the same at around 110-115 bar for much better tunability and a higher shot count.

The fx plenum is a good choice for .22 and .25 but guys that want the best performance .30 or .35 should get the larger $150 plenum from Michal Osyda.

Sorry chuck for my post because I understand that you are asking results only for Fx pp . 
But I will agree with Heavy impact regarding the power plenum from Poland . 

My set up is this 
Fx impact x 30 cal. 

1) pp from Poland 

2) Extra high pressure regulator huma 165-200 bar.

3) hammer weight 7 grams .

4 )double transfer port ( Ernest style but the first one not the latest with the pin probe style) 

5) valve seat 6.8 

6) I install LW barrel 71 cm length 1:16 twist Unchocked . ( the main time still I was waiting the Fx slug liner . I have receive it now but still I didn’t try it ) The LW barrel is same diameter like the Fx sleeve . Is a little heavier for sure but in high pressures maybe is working better than the Fx liner regarding armonics.


I have post my results end of last October again in the forum . The accuracy with LW barrel was extremely good . I was shooting 65 grains NSA slugs with half moa at 80 yards . At 50 yards was many groups almost one hole. Unfortunately I am resident in another country and I am shooting my gun only in my vacations 2-3 times per year so I didn’t have the time to shoot longer distance . 

I have set the regulator at 185 bars. 
I have max HST screw . 
I really don’t remember what line was the valve adjuster . 
Speed with 65 gr NSA 940-950 f/S 

Even with this high pressure ( relatively) after 1200 rounds I didn’t have any leaks or any kind of problems with my impact . ( gun was new out of the box . I made all the modes in a new gun without shoot not even one pellet ! )

“Heavy impact “ I see that you have same results with little heavier slug (66 gr) but regulator only at 150!bar. 
Do you believe that the reason is the LW barrel ? I mean the Fx slug liner is faster than a LW barrel ? 
Or the transfer port ? I remember last year if i am not wrong that you insist to a simple tp and not double for better air path .


Anyway next time I will try my new 700 Fx slug liner and simple enlogated TP to see the difference.

I want to mention that the gun with this settings is a beast. I was shooting at 70 yards small apples in a tree and honestly I could not find not even a piece on the ground . Was evaporated . You could see just steam in the air after the hit . I am trying to upload a video here but I can’t . I don’t know what I am making wrong . Only pictures . 
I will post some pict from the barrel project and the gun . 

I am trying to upload a video here but I can’t . I don’t know what I am making wrong . Only pictures .

Click to expand...

Use youtube or imgur.com to host your video then post the url here.

I believe the profile of my single port along with the top portion of the pellet probe being removed gives higher velocity. My pellet probe is also thinned and knife edged where material was removed and material was removed from the ceiling of the brass inlet to allow unrestricted flow in the turn. The vertical port in the rear block is opened to 8mm.

“ Heavy impact “ 

Thanks for your reply. The transfer port of rear block from the factory is 7mm? 
How did you open the tp in rear block to 8mm? 
long time before I order a rear block and I receive it right now. I was thinking to drill it from downside through the hole of the screw that tights the valve house with a drill 8 mm but after I need to tap it again with new threads and bigger screw so I can tight again properly the valve house. 
Did you made the valve house tp as well 8 mm? 
what do you mean material removed from the celling of brass inlet ? 
do I have to make thinner the walls of the brass inlet ?To remove material internal ? Sorry for my terrible English language. I am trying to understand . 

“ Heavy impact “

Click to expand...

Reach in from the threaded hole and yes the valve housing matches.

The brass is thinned from the inside about 1mm but only at the top just above and forward of the vertical transfer port. This only works if the top portion of the pellet probe is removed.

I do this with a li-ion rotary tool and a carbide burr, second one from the right in pic ⑲.

Thank you “ Heavy impact” 

We really appreciate all the knowledge you are offering in this forum as many other members. I want to mention that I start preparing all the parts for the necessary modes for my impact long time before I receive my gun only by watching your advises ( yours and all the other members ) and when I receive the gun every part seems to be so familiar to me like I have the gun for years . For sure I faced some issues because is different the theory from the practice but I never have the need to send my gun to a gunsmith . As they say everybody who byes an impact should be ready to pass through this process . But after that you have the confidence to figure out every problem .Anyway sorry from everybody if we are of topic with this discussion .
I am really interesting to see results and settings with the original Fx power plenum for 30 cal. from other members. 

Thanks again “Heavy impact “ 

and thank you Chuck for opening this thread. 

I added the power plenum today and tried my 25 cal barrel 700. Reg at 120 shooting 33,95 grains . Very happy with the st.dev after the installation. 

Not sure about others, but I'm just as interested in efficiency increases with the new FX PP or Polish Plenum as I am with the power gains. I'd like to see the before and after efficiency with the .30 caliber pellets (44.75 grain). We've seen all this info on power gains and such, and have "heard" about efficiency gains, but numbers haven't been posted (or I haven't seen them). Easy calculator below...

PCP Airgun Efficiency Calculator

Havent done this in .30, but last time out ratting. 240-200 bar 81 shots at 860, 15.89 (hades) is 1.8. Is that good for a medium power tune?

Shot 3 mags less 3 pellets.

Damn good... Anything over 1.4 is considered Excellent...

Damn good... Anything over 1.4 is considered Excellent...

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Yeah im sure won't be as efficient in .30, next time i have it in .30 ill run the numbers. You're looking for numbers around the 80fpe in .30 for the test?

Yes, since that's what most shooters use in Competition with pellets. The 44.75 grain JSB between 850 and 910 FPS seems to be the most accurate and minimizes flyers in most airguns.

Not sure about others, but I'm just as interested in efficiency increases with the new FX PP or Polish Plenum as I am with the power gains. I'd like to see the before and after efficiency with the .30 caliber pellets (44.75 grain). We've seen all this info on power gains and such, and have "heard" about efficiency gains, but numbers haven't been posted (or I haven't seen them). Easy calculator below...

PCP Airgun Efficiency Calculator

Click to expand...

FX is advertising shot count...

I added the power plenum today and tried my 25 cal barrel 700. Reg at 120 shooting 33,95 grains . Very happy with the st.dev after the installation.

Click to expand...

Wow. Fantastic.

FX is advertising shot count...

Click to expand...

I’ve seen that. Thanks. Doesn’t provide real efficiency numbers though...

I’ve seen that. Thanks. Doesn’t provide real efficiency numbers though...

Click to expand...

I wish I could be more thorough like some of you guys but I'm not. I don't pay much attention to that stuff because I just want to blow the she-ot out of a squirrel or two and I own an electric pump.