FX Rear air leak

[speedy]

Good day
I need some advice please. I bought a new Fx impact 700mm .22 m3 fitted with a slug liner and slug kit (pinprobe/tungsten hammer and lighter valve return spring)
The 1st reg is on 150 bar and the 2nd reg on 108 bar. Shooting 25 grain 218 H&N slugs 984 fps and grooping is very good at 100 meters. Hammer on 12, mico at 3.75 and the valve 3 turns out. Shooting 30 grain H&N at 935 fps but with a problem

The problem i have is, once you open the valve 4.5 turns and put the hammer on 16 and shoot a shot there's an air leak at the rear end at the magazine/power block rear/barrel area ONLY when you pulling the cocking lever back to load a slug. You can hear it clearly it is not the plenum filling with air. Once you push the cocking lever forward the leak stops. If you turn the valve in say to line 3 the leak stops.
If you just pulling the cocking lever back without shooting a shot, there is no leak. The gun is also not leaking air when standing for days.
Could it be the lighter valve return spring, causing the valve to stay open longer.
Would you recommend to put the stronger original valve return spring back.
Regards

 

[F6Hawk]

Good day
I need some advice please. I bought a new Fx impact 700mm .22 m3 fitted with a slug liner and slug kit (pinprobe/tungsten hammer and lighter valve return spring)
The 1st reg is on 150 bar and the 2nd reg on 108 bar. Shooting 25 grain 218 H&N slugs 984 fps and grooping is very good at 100 meters. Hammer on 12, mico at 3.75 and the valve 3 turns out. Shooting 30 grain H&N at 935 fps but with a problem

The problem i have is, once you open the valve 4.5 turns and put the hammer on 16 and shoot a shot there's an air leak at the rear end at the magazine/power block rear/barrel area ONLY when you pulling the cocking lever back to load a slug. You can hear it clearly it is not the plenum filling with air. Once you push the cocking lever forward the leak stops. If you turn the valve in say to line 3 the leak stops.
If you just pulling the cocking lever back without shooting a shot, there is no leak. The gun is also not leaking air when standing for days.
Could it be the lighter valve return spring, causing the valve to stay open longer.
Would you recommend to put the stronger original valve return spring back.
Regards

So if you pull the cocking lever back, and hold it back, you can hear air leaking? Can you see any gauge dropping pressure while doing so?

 

[Bigragu]

Your valve rod over traveled forward which caused the valve stem(the tiny head you see in the mag slot) to move out of its comfort zone within the power plenum, and caused the 2.2mm x 1mm DURO 70 o ring to get nicked or disintegrate. Thst needs to be replaced. Hopefully you’re saavy with tear down as you’ll have to completely tear the gun down a good 75% to get that repaired. When it first happened you probably heard a tiny pop noise.

 

[speedy]

So if you pull the cocking lever back, and hold it back, you can hear air leaking? Can you see any gauge dropping pressure while doing so?

Hi. Yes if you hold the cocking lever back you can see the Bottle pressure gauge dropping. Once you push the cocking lever forward the leak stops.
This only happens when you turn the valve open and after a shot has been fired

 

[speedy]

Your valve rod over traveled forward which caused the valve stem(the tiny head you see in the mag slot) to move out of its comfort zone within the power plenum, and caused the 2.2mm x 1mm DURO 70 o ring to get nicked or disintegrate. Thst needs to be replaced. Hopefully you’re saavy with tear down as you’ll have to completely tear the gun down a good 75% to get that repaired. When it first happened you probably heard a tiny pop noise.
View attachment 439503

Thanks. It was leaking since day one, when i started to tune the gun. Didn't hear any popping noise at that time.

 

[Ca_Varminter]

Well your M3 is leaking air pass the main-valve.
You can hear the air since the Probe isn't sealing the breach...
Did you say it stops if you increase the return spring pressure??
This can be cause by debris or damage to the valve face.

BTW the small O-ring is only seal air from escaping the tail section, when you fire your m3.

 

[speedy]

Well your M3 is leaking air pass the main-valve.
You can hear the air since the Probe isn't sealing the breach...
Did you say it stops if you increase the return spring pressure??
This can be cause by debris or damage to the valve face.

BTW the small O-ring is only seal air from escaping the tail section, when you fire your m3.

What I have noticed is, that it is only leaking air when the valve is opened past 4 lines, and only after you fired a shot pulling the cocking lever back. Once you push the cocking lever forward the leak stops
Once you close the valve let's say to line 3 (where my tune is hammer on 12/micro on 3.75 and valve on 3) the cun is 100%.

 

[Ries]

Is a tungsten hammer needed for this? i use the lightest huma hammer and shooting 23 grains at 940 fps out of a impact compact

 

[Ca_Varminter]

What I have noticed is, that it is only leaking air when the valve is opened past 4 lines, and only after you fired a shot pulling the cocking lever back. Once you push the cocking lever forward the leak stops
Once you close the valve let's say to line 3 (where my tune is hammer on 12/micro on 3.75 and valve on 3) the cun is 100%.

By increasing the Valve sealing spring pressure and it seals...
It does sound like the sealing face of the valve has slight amount of damage or is deformed..

 

[Trucker3573]

You bought it brand new or used …new to you ? You probably smacked it too hard. 3.75 micro with a tungsten hammer is waaay too much for 108 bar.
Also, I had a similar problem on a used one all decked out for power to shoot slugs. It was run at really high pressure so the valve pin got “used” to sealing at this high pressure. Therefore it wouldn’t seal at low pressure and did similar things as you described.

 

[LDP]

Is the air leaking from the breech? If its leaking from the breech as in where the pellet goes its the valve seat that @Ca_Varminter mentioned.

 

[speedy]

Is a tungsten hammer needed for this? i use the lightest huma hammer and shooting 23 grains at 940 fps out of a impact compact

I have removed the tungsten hammer and fitted a 7.4 gram hammer. Shooting 25 grain slugs at 984 fps