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

[bigHUN]

It helps if you increase the hammer weight and restrict the valve travel from valve adjuster. The extra inertia over powers the sticking of O ring and valve adjuster doesn't allow to generate more power than desired.

Looks like you missing something......the valve adjuster is YES playing a role with output power. +/- 1 mm is a huge difference in dwell time.

The moment of inertia (in my setup) will for sure will break the sticking on the PUR90. My hammer is 24.6 gram + a 55.3 spring generates serious power. This why I busted the 2mm oring and needed a rubber ball back into the valve.

 

[mubhaur]

It helps if you increase the hammer weight and restrict the valve travel from valve adjuster. The extra inertia over powers the sticking of O ring and valve adjuster doesn't allow to generate more power than desired.

Looks like you missing something......the valve adjuster is YES playing a role with output power. +/- 1 mm is a huge difference in dwell time.

The moment of inertia (in my setup) will for sure will break the sticking on the PUR90. My hammer is 24.6 gram + a 55.3 spring generates serious power. This why I busted the 2mm oring and needed a rubber ball back into the valve.

I understand that you are referring to the O ring at the magazine side of valve rod that has been busted.

Putting the rubber ball in the valve spring is good to do.

I still do not feel that the cause of busting your O ring is the heavy hammer hit.

However you may try 80 shore or 90 shore O ring there which got busted.

Bhaur 

 

[Vetmx]

Place NBR90 there instead of PUR90. All this thread and it seems you make the old mistakes which makes me sad.

Seeker did the viton hold up still or did u go to nbr90 already

I have over 600 shots with the Viton in my gun. No problems yet.

Good to hear I'll probably use viton then since I have some on hand

Just make sure you build a peek washer. If you don’t, that Viton is doomed to a very short existence. 

 

[Airgunmann]

Place NBR90 there instead of PUR90. All this thread and it seems you make the old mistakes which makes me sad.

Seeker did the viton hold up still or did u go to nbr90 already

I have over 600 shots with the Viton in my gun. No problems yet.

Good to hear I'll probably use viton then since I have some on hand

Just make sure you build a peek washer. If you don’t, that Viton is doomed to a very short existence.

I will just it's shooting so we'll and was waiting on 720 pp before I tear into it 

 

[Seeker]

It's a pity that the progress goes along with the power but the basics are not covered correctly:

https://youtu.be/SFsuwZnUZOU

Question is when FX is going to address the oring stiction issue which affects both Mk2 and M3.

 

[cmatera]

I agree.

 

[Bigragu]

I think these rubber balls within the valve knob of the M3 has to play part in velocity swings and first shot problems. For the ones that don’t know, these 

balls in 4mm and 4.75mm back to back are responsible for shock absorbing onto the striker that the C1 hammers on. You can see the 4mm ball is near flattened, and the 4.75 one partially flattened. What I noticed is after leaving them out for awhile they start to retain their original shape somewhat, which leads me to believe that’s a shorter valve rod throw after the guns been sitting, then as they start to flatten shot after shot, the valve rods throw is now longer.

I used to boast low extreme spreads, like 5 FPS in 36 shots and 14 FPS in over 90 straight shots, then I noticed over time my low spreads started to widen. There was also more of a jolt up front following the shot.



ive since replaced these balls with DURO 75 viton, solid rubber cord, that fits perfectly within the inner walls where the balls would go into. My consistency is back and the sound rapport of the shot has dropped some. I’m now staying steady between 1010 and 1016 shooting the monster redesigns in 22 cal

 

[cmatera]

I'm going to try one rubber ball in the spring, and one where it is, to deaden the little tink sound.

 

[mubhaur]

https://youtu.be/aKKLzpWPViE

This video may be helpful. 

Bhaur

 

[Chris_Fourt]

Sure, we are all here to make the gun better.

I truly believe that the following items contribute to the issue:

-PUR90 oring and its increasing stiction,

- extrusion of mentioned oring,

- stiff valve return spring,

- delrin valve poppet.

Some combinations of them amplify the issue more. Given Impact valve design we cannot eliminate the problem entirely. We can just minimize it to the insignificant level.

In my opinion the following should be done to achieve the highest consistency possible when it comes to the first shot after valve inactivity time (most important comes first):

- peek backup washer should be installed to prevent from oring extrusion,

- PUR90 oring should be replaced with NBR90/80 or Viton90/80 (the latter one may not be good enough abrasion resistance wise but it has the lowest stiction among three mentioned compounds),

- peek valve poppet should be installed,

- valve return spring should be balanced - not too stiff and not too weak. The original spring seems to be more one a stiff side. The Huma power kit one is too weak unless you have 700mm barrel.

@mubhaur, what is the specification of the valve return spring which you find optimal?

Great work Seeker, I'll try the NBR90 oring and a weaker spring (probably the one that comes with the 0.30 caliber). Do you have any further information about the long-term performance of the NBR90 oring?
Cheers!
JCF

 

[Seeker]

I have no issues at all even with Viton80 and NBR90 should last even longer. @Vetmx also used/uses Viton and he made hundreds (thousands maybe) of shots with it without any problem.

 

[Airgunmann]

Ok so I just got the new 720 plenum for the mk2 upgrade that I ordered about 6 months ago the o ring in the end that supposedly had the taper is installed and it isn't coming out using the rod or something a tad larger to push it out I wanted to see if fx addressed the issue it's a white o ring and seems pretty hard did the old one just slip out of the pinch point easily the kit came with the plenum a new valve rod valve adjuster and the power tube I believe al ready in place and all the o-rings in place

 

[Airgunmann]

So I removed the o-ring and it appears there are two o-ring

 

[Airgunmann]

So the seat still has a small taper in it I'm going to machine just a flat piece of peek and install it before I install it on the gun and will use viton o-ring and another o-ring to hold it all in place appears to be the taper from a drill bit If I had the correct size and long enough mill bit I'd think about milling it flat but I don't looks like there is plenty of space for a peek spacer so I'll do that and a thick enough o-ring should seal everything correctly

 

[Vetmx]

Make sure once your peek disc is down in there then the Viton then the little black one, that the black one isn’t visible in your plenum recharge hole. If you can see the black one it’s time to make the peek tapered disc thinner.

 

[bigHUN]

Also, mirror finish on the Valve Rod. No need the entire length but about the position of the orings +/- 10 mm

 

[Vetmx]

What bigHun said and while you’re in the bling mode, mirror where your hammer rides. Do both and you’ll be +10.

 

[Seeker]

Ok so I just got the new 720 plenum for the mk2 upgrade that I ordered about 6 months ago the o ring in the end that supposedly had the taper is installed and it isn't coming out using the rod or something a tad larger to push it out I wanted to see if fx addressed the issue it's a white o ring and seems pretty hard did the old one just slip out of the pinch point easily the kit came with the plenum a new valve rod valve adjuster and the power tube I believe al ready in place and all the o-rings in place

I would not count on FX in that term. They are aware of the issue as @mubhaur informed Fredrik but he possibly prefers to drive his McLaren.

 

[Airgunmann]

Well I got my 720 plenum for mk2 made a peek washer now I need to find viton o-ring the correct size any one know the correct size of viton o-ring and where you got it from thanks

 

[Chris_Fourt]

Well I got my 720 plenum for mk2 made a peek washer now I need to find viton o-ring the correct size any one know the correct size of viton o-ring and where you got it from thanks

Hi Airgunmann, the o-ring size is 2.84x2.62
Cheers