Tuning Low fps the first 10 shots FX impact mk2 compact.25

[asgardpark]

Hi!
I have a weird problem on My impact mk2 i need to shoot about 10 shots befor it get Up to Speed if i left it over night.
Its currently tuned to shoot 30grain h&n slugs in 932-935 and the regulator is about 135-140bar the Valve adjuster between 4and3 and hammer is set to match the regulator. When i left it over night it usaly shoots around 910 and climb up to 935 in 10 shots.
The regulator stays on the same pressure all Night. I tested to degas the gun before I shot it and the it shot about 925 but still I hade to shoot a couple of shots befor I get up to speed.
Any one got an idea what am doing wrong?
//Daniel

 

[JohanG]

I have the same issue. Watching this thread.

 

[mubhaur]

I have done this solution. Now my Impact takes only one shot. Previously it used to take eight shots.

This is due to a flaw in design of plenum that causes the O ring to extrude.

Bhaur

 

[asgardpark]

So if I only change the oring the problem will continue?
I don't have the machine or the knowledge to make the part. If it's a design flaw FX should address this and make a fix

 

[douger]

1-was it always like that? 2 rebuild the reg

 

[nervoustrig]

Here’s a link to the lengthy thread where we troubleshot and brainstormed on the issue:

Tuning - FX Impact Mk2/M3 - slower first shot - no reg creep - quasi-scientific analysis

Hi guys, Welcome everybody. This is my first post here. I have a problem with my Impact Mk2 PP .30. The reg pressure is 145 bars. When I shoot shot after shot then my v0 is 260m/s. However, when the gun sits for a couple of hours then the first shot is 250m/s despite the exact same reg...

www.airgunnation.com

 

[Scottsairgunning]

Hi!
I have a weird problem on My impact mk2 i need to shoot about 10 shots befor it get Up to Speed if i left it over night.
Its currently tuned to shoot 30grain h&n slugs in 932-935 and the regulator is about 135-140bar the Valve adjuster between 4and3 and hammer is set to match the regulator. When i left it over night it usaly shoots around 910 and climb up to 935 in 10 shots.
The regulator stays on the same pressure all Night. I tested to degas the gun before I shot it and the it shot about 925 but still I hade to shoot a couple of shots befor I get up to speed.
Any one got an idea what am doing wrong?
//Daniel

 

[Scottsairgunning]

Temp sometimes can make a difference one of my impacts is a little fussy when it's cool out until it warms up

 

[asgardpark]

does it all happen to all impact or are only some affected? if you are lucky would it work to upgrade to a m3 plenum? for me I have to sell it as you can not buy an upgraded part of FX and I can't make the parts my self

 

[Vetmx]

No, my M3’s do it just like my MKll’s did it. You either have to address it or live with it. I couldn’t live with it so it had to be addressed or guns sold.

 

[asgardpark]

Thanks for pointing me in right direction!
I managed to solve my issue by changing the pur90 oring to an nbr90. My valve rod had a very rough surface so I polished it and i added a huma hammer weight and huma hammer spring. I also noticed that the valve return spring was in bad condition so i swapped that to. After the first night it shot 884fps with the king heavy mk2, waited 2 days the first shot was 886fps, took a shot this morning 884fps.

 

[mubhaur]

Thanks for pointing me in right direction!
I managed to solve my issue by changing the pur90 oring to an nbr90. My valve rod had a very rough surface so I polished it and i added a huma hammer weight and huma hammer spring. I also noticed that the valve return spring was in bad condition so i swapped that to. After the first night it shot 884fps with the king heavy mk2, waited 2 days the first shot was 886fps, took a shot this morning 884fps.

Initially I did the same. With high powers it works. The reason being the NBR doesn't get flexible after some use hence not notable extrusion.

The other way is to increase the hammer strike and restrict the valve travel by tightening valve adjuster.

But ultimately the comfort I had with FX impact mk1 with O ring from front style plenum could not be achieved specially with 18 grain .22 pellets.

So I made the front plenum part in mk1 style. It took some time to break in but after breaking in, I enjoy my M3 much more than before.

 

[jbravo103]

Thanks for pointing me in right direction!
I managed to solve my issue by changing the pur90 oring to an nbr90. My valve rod had a very rough surface so I polished it and i added a huma hammer weight and huma hammer spring. I also noticed that the valve return spring was in bad condition so i swapped that to. After the first night it shot 884fps with the king heavy mk2, waited 2 days the first shot was 886fps, took a shot this morning 884fps.

Did you add the PEEK backup washer? My M3 is still all stock and I’m getting 30-40 fps low on first shot. Takes at least 5 shots to get back up to set velocity.

 

[Vetmx]

There are a couple ways to try to skin this cat but probably only two ways to do it properly. If you decide to try to overcome the sticking stock PUR oring by blasting it with a heavier hammer and spring, you’re going to have to control that with your valve knob. If you’re not shooting with very high reg pressures, you’re going to punish the valve spring and if you have a M3 the rubber balls also. If you just stick a Viton or NBR oring in there without a peek washer, that things lifespan is going to be short. That’s why FX used that big nasty PUR. It can handle extrusion without coming apart. So, either you peek washer/90 it or replace the plenum piece with a mubhaur piece.

 

[Seeker]

Actually that PUR90 oring suffered from extrusion in my case. I even posted a picture of that in the mentioned thread. A peek washer or mubhaur's plug is a must regardless of the oring used.

 

[Trucker3573]

No impact and these threads ensure I never will own one. Absolutely unacceptable that one, this is the performance out of the factory and two that a new owner should have to lift a finger to correct it after spending 2k or more. Guess people are more patient than me.

 

[rsfrid]

Don't have that problem with my RAW.

 

[SpiralGroove]

Don't have that problem with my RAW.

My two RAW's took 1 shot for the regulator to recover after sitting overnight. Changed the regulator's seat to peek and now every shot consistent no matter how long they sit.

 

[Vetmx]

Actually that PUR90 oring suffered from extrusion in my case. I even posted a picture of that in the mentioned thread. A peek washer or mubhaur's plug is a must regardless of the oring used.

Yes but the PUR won’t fail as quickly as a Viton or NBR if you skip the peek disc. I am kinda curious how long a NBR 90 will last being pressed into that cone by 140b.

 

[jbravo103]

I don’t have the tools or equipment to make a PEEK washer for the plenum. Are there any members making them to purchase?