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fx impact power plenum issue

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M

milanilo

Member
Apr 19, 2020
27
1
saudi, Saudi Arabia
i have two impacts mk2 .22 cal

1 with power plenum installed by fx 

1 came with out pp , so i ordered fx impact power plenum complete kit ( includes hammer weight + spring + valve ) and install it.

i noticed the hammer tension is still the same without pp , the fx impact mk2 with factory installed pp has much more hammer tension room .

with my impact factory installed pp i can get 970 fps using HN 25 g slugs ( hammer is not even maxed out- 130 reg )

with other mk2 pp i barely get 920 fps ( maxed out hammer - 140 till 150 reg )



i noticed a difference in hammer spacing between the two.

plz advise me if i am missing something 


 
I don't know why FX has changed the hammer's spring from 57mm to 52mm. And what make things more complicated, the new valve's spring which is too strong for anything over 130 bar. 

I think they should have used the 57mm and included 2 or 3 different springs for the valve.
Click to expand...

maybe if i installed the 57mm again i will get more power
1f914.svg
Click to expand...

Yes you should.
 
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Don't do anything until you collect one more piece of information. Could be a difference you haven't noticed yet.

Measure the length of the sliding Hammer Spring Tension Adjuster on each gun. I would bet the one on the gun where you installed the PP is 18mm long, and the one on the gun that FX installed the PP is 16mm (if so, they probably changed it out when they did the install). FX modified the length of this piece to allow another 2mm of adjustment to aallow more hammer spring tension preload. My guess is because of the new lighter 52mm spring used today, as the extra 2mm will allow more preload.

Check it and let us know. You might be comparing apples and oranges.
 
Upvote 0
Don't do anything until you collect one more piece of information. Could be a difference you haven't noticed yet.

Measure the length of the sliding Hammer Spring Tension Adjuster on each gun. I would bet the one on the gun where you installed the PP is 18mm long, and the one on the gun that FX installed the PP is 16mm (if so, they probably changed it out when they did the install). FX modified the length of this piece to allow another 2mm of adjustment to aallow more hammer spring tension preload. My guess is because of the new lighter 52mm spring used today, as the extra 2mm will allow more preload.

Check it and let us know. You might be comparing apples and oranges.
Click to expand...

u r absolutely right 

so what should i do in this case to get higher fps or how to change this piece ( can i buy it separately )

1591301014_4436905485ed953961734d6.55926577.jpg


1591301133_20576061885ed9540d6e6d00.61562626.jpg
 


 
Upvote 0
Thought that might be contributing here. First and foremost, call FX USA and ask if they have them in stock yet. I doubt it, as I'm supposed to be on a waiting list to get a call when they have them, but have not heard anything yet. However, there is always the chance they have forgotten or their flag did not come up. I haven't worried much, because I modified my 18mm ones on our existing rifles when I installed the PPs.

I removed mine and mounted them on a CNC router table, then machines the front edge profile back 2mm. Exactly what I'd have if I bought new ones, except the front edge is now bare shiny aluminum vs. a black anodized finish. You can use whatever method to file, grind or cut the edge back the 2mm, but if you do this, be sure and radius the corners, or they will restrict the forward movement of the HSTA slider in its channel, and you won't get the full 2mm of additional tension preload. Also, it matters which edge you remove material from. Pay attention to that. Remove material ONLY from the end you put your allen wrench in to adjust the HSTA screw.

I think everyone claims you have to use the old 57mm hammer spring because very few DIY installs have replaced/modified the HSTA slider, and they can't get quite enough preload to get to the power/velocity they want. That extra 2mm of preload is a good extra bit of power/velocity, and with it, I feel the 52mm hammer spring is fine until I start wanting to push heavy slugs and such. For now, I just want an accurate pellet rifle, and in the future, I may want to try field target at .177, and that would be very easy to overpower. If you have to stay with the 18mm slider, I would probably consider using the original 57mm spring.

However, I have seen velocities in the 860s to 870s at a reg pressure of 90-95 bar, and not even close to being in that extra 2mm that the 16mm HSTA slider gives you. But, once you get the reg pressure up a bit more, you're going to need that extra 2mm of adjustment range or the 57mm spring.

Hope this helps.


 
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Upvote 0
Thought that might be contributing here. First and foremost, call FX USA and ask if they have them in stock yet. I doubt it, as I'm supposed to be on a waiting list to get a call when they have them, but have not heard anything yet. However, there is always the chance they have forgotten or their flag did not come up. I haven't worried much, because I modified my 18mm ones on our existing rifles when I installed the PPs.

I removed mine and mounted them on a CNC router table, then machines the front edge profile back 2mm. Exactly what I'd have if I bought new ones, except the front edge is now bare shiny aluminum vs. a black anodized finish. You can use whatever method to file, grind or cut the edge back the 2mm, but if you do this, be sure and radius the corners, or they will restrict the forward movement of the HSTA slider in its channel, and you won't get the full 2mm of additional tension preload. Also, it matters which edge you remove material from. Pay attention to that. Remove material ONLY from the end you put your allen wrench in to adjust the HSTA screw.

I think everyone claims you have to use the old 57mm hammer spring because very few DIY installs have replaced/modified the HSTA slider, and they can't get quite enough preload to get to the power/velocity they want. That extra 2mm of preload is a good extra bit of power/velocity, and with it, I feel the 52mm hammer spring is fine until I start wanting to push heavy slugs and such. For now, I just want an accurate pellet rifle, and in the future, I may want to try field target at .177, and that would be very easy to overpower. If you have to stay with the 18mm slider, I would probably consider using the original 57mm spring.

However, I have seen velocities in the 860s to 870s at a reg pressure of 90-95 bar, and not even close to being in that extra 2mm that the 16mm HSTA slider gives you. But, once you get the reg pressure up a bit more, you're going to need that extra 2mm of adjustment range or the 57mm spring.

Hope this helps.

Click to expand...

thank u very much for ur time and effort writing a very helpful advice 

i only needed extra fps since i started using slugs , i only use .22 for slugs 

i think i will install the old 57mm + modified pellet probe & brass


 
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