FX Impact M3 Loss of Velocity

[MattD88]

Hi All

I am in need of help as my 16 month old FX Impact M3 600mm barrel (.22 / 5.5mm) has suddenly lost velocity.

FACTS:
(1). M3 - .22 - 16 months old - 4000 pellets shot - never had a slug in the barrel

(2). All original factory settings - Never adjusted, tuned or changed.
Hammer Spring = 16 (Factory - Never adjusted!)
Micro Adjuster = 1.5. (Factory - Never adjusted!)
Valve = 4.5 turns. (Factory - Never adjusted!)
First Regulator = 150 BAR (Factory setting)
Second Regulator = 75-78 BAR. (Factory - Never adjusted!)

(3). Velocity (JSB 18.13 gr) was, for 16 months always around 870fps on the factory settings as shown above.

(4) About 3 weeks ago velocity dropped to 840 fps

(5) About 2 weeks ago velocity dropped to around 800 fps

So, when I noticed 800 fps, I now decided to try increasing the regulator pressure (bear in mind, that until now all settings were still factory and had NEVER BEEN touched). Increased the second regulator pressure to 95 BAR and velocity dropped to around 720 fps with hammer spring on 16. As the velocity had decreased further I decided to return the regulator to original setting.

(6). Removed bottle, depressurised gun and reset regulator to original 75-78 BAR. Ran FX Radar chronograph over 8 shots and velocities were: 779, 784, 800, 821, 810, 823, 786, 810. Spread of 44, Standard Deviation of 17.1.

(7) I stress, this rifle has NOT had any tuning or changing of the factory settings (as above) because it gave me the accuracy and velocity I required. However, for some reason the velocity has dropped and the extreme spread is indeed extreme!

Has anyone got any ideas. Something has gone wrong somewhere.

Thanks

Matt

 

[weevil]

There’s a good chance that one of many orings is kaput. If you’re not comfortable tearing into it, it’s best to contact FX for service.

 

[igolfat8]

Mine did the same thing. It was the C3

 

[madeintheuk]

If you’re reg gauge is staying constant, the most likely culprit is your c3 coming loose

 

[Butch]

I do agree with most saying C3 coming loose but before you go that route I would start with installing a new breech seal and checking the pellet probe to see if it loosened up.

Butch

 

[igolfat8]

I do agree with most saying C3 coming loose but before you go that route I would start with installing a new breech seal and checking the pellet probe to see if it loosened up.

Butch

Before you do that just lay a Kleenex across the breech area, cock and close the bolt then fire in a safe direction while watching for any movement of the tissue. That will tell you if the breech o ring needs replaced.

 

[MattD88]

Before you do that just lay a Kleenex across the breech area, cock and close the bolt then fire in a safe direction while watching for any movement of the tissue. That will tell you if the breech o ring needs replaced.

 

[MattD88]

Hi

Thanks for all the suggestions to date.

When I removed the bottle to depressurise the gun in order to reset the reg to 75-78 BAR, I also took the opportunity to remove the barrel and I replaced the breech seal as I thought it may be the cause of the issue. However, the breech seal was OK, but the the gun now has a new one.

I had a thought it may be the C3, but according to the parts diagram for the M3, there does not appear to be a C3 at all. Does the M3 have an equivalent to the C3 which was in earlier models of the Impact?

Thanks
Matt

 

[rappert]

The C3 bumper is integrated into the hammer on both the mkII and mkIII. It is also possible your hammer seat is loose and slowly backing it's way out causing the valve to open less and less.

 

[Emu]

Second Regulator is giving more pressure, so hammer may not open correctly the valve.

Regulator has to be taken out to lubricate O'rings, so regulator may work properly.

 

[Headshots]

Hi All

I am in need of help as my 16 month old FX Impact M3 600mm barrel (.22 / 5.5mm) has suddenly lost velocity.

FACTS:
(1). M3 - .22 - 16 months old - 4000 pellets shot - never had a slug in the barrel

(2). All original factory settings - Never adjusted, tuned or changed.
Hammer Spring = 16 (Factory - Never adjusted!)
Micro Adjuster = 1.5. (Factory - Never adjusted!)
Valve = 4.5 turns. (Factory - Never adjusted!)
First Regulator = 150 BAR (Factory setting)
Second Regulator = 75-78 BAR. (Factory - Never adjusted!)

(3). Velocity (JSB 18.13 gr) was, for 16 months always around 870fps on the factory settings as shown above.

(4) About 3 weeks ago velocity dropped to 840 fps

(5) About 2 weeks ago velocity dropped to around 800 fps

So, when I noticed 800 fps, I now decided to try increasing the regulator pressure (bear in mind, that until now all settings were still factory and had NEVER BEEN touched). Increased the second regulator pressure to 95 BAR and velocity dropped to around 720 fps with hammer spring on 16. As the velocity had decreased further I decided to return the regulator to original setting.

(6). Removed bottle, depressurised gun and reset regulator to original 75-78 BAR. Ran FX Radar chronograph over 8 shots and velocities were: 779, 784, 800, 821, 810, 823, 786, 810. Spread of 44, Standard Deviation of 17.1.

(7) I stress, this rifle has NOT had any tuning or changing of the factory settings (as above) because it gave me the accuracy and velocity I required. However, for some reason the velocity has dropped and the extreme spread is indeed extreme!

Has anyone got any ideas. Something has gone wrong somewhere.

Thanks

Matt

When you increase 2nd reg pressure you need more hammer spring also or you will loose velocity. Your hammer spring adjustment may have backed off over 4k rounds.

 

[Vetmx]

Your C52, formerly the C1 has probably been beaten loose. Doesn’t take long to check. Then move on to more mysterious possibilities.

 

[MattD88]

Hi Everyone

Thanks for the very worthwhile suggestions - very much appreciated.

Here is my next plan of attack:

(1). Watch some good videos on dismantling the M3.

(2). Dismantle and check the C52 (hammerseat) and check various orings and seals etc and replace where necessary. And then re-perform velocity checks.

Something which mystifies me is this: I understand that increasing the 2nd regulator pressure necessitates an increase in the hammerspring - as stated by "Headshots". However, when my hammerspring wheel is already on 16 and the micro-adjuster is at 1.5 - which means that the hammerspring is very close to being maxed-out - how can I further increase the hammerspring if I should want to increase the reg pressure to say 100BAR to say shoot the 18.13 pellets at 1000fps? (My actual need is 870fps as I find this ideal for these pellets.)

Thanks to all and the very best to you and yours for 2023.

Matt

 

[Vetmx]

You are close to being maxed out when your wheel is on 16 and your micro is on 3.5. If you up your reg, leave the wheel on 16 then use the micro to find your new plateau speed. You always and can only tune down from your regs plateau speed. By leaving your wheel on 16 when you find that speed, you will always have that as a reference. For example. The situation you are in is a good one. If your gun suddenly starts acting whacky and you know because you wrote it down that your plateau speed with the valve wide open and your wheel on 16 was 950fps, its real easy to click your wheel back to 16 and open the valve to check. Your final tune might be with the wheel on 13 and your valve set at 10mm. But knowing that 16 is the plateau speed for your reg setting makes life with this gun very simple when it goes off it’s nut.