FX Impact M3 Sniper .25 700mm Erratic fps

[Kevgun]

Hi Guy/Gals this is my first post , so go easy please.

I am in the UK and own several other air rifles / rim fires/ centre fires etc, so it's not my firs day at school.



Bought this rifle brand new in December last year, it has been shooting fine, but all of a sudden it's started varying it's speed, I have a digital gauge on the 2nd reg and I have it set to 130 bar I was shooting H&N 34 gr slugs at 960 fps, when you fire it the gauge drops from 130 to 127 then returns to 130 bar within 6 seconds I shot over 2 chronographs just to confirm that it's not my chronograph. but now its changing from 960fps down to 780fps then 900fps but the reg pressure remains constant, but it won't shoot a group which is understandable concidering the variation in speed. so does anybody have any ideas?

TIA

Kevgun

 

[Bigragu]

So from December of last year tell us all that you have personally done to your gun. Could be a lot of things possibly caused by the owner so that’s why I ask. Things just don’t happen all of a sudden, unless it’s the C1 unthreading out of spec or some type of airflow leak/restriction going on.

It’s the internal modifications I’m inquiring about, not bling bling add ons

 

[Kevgun]

Hi Bigragu, I see what you mean, I have replaced the standard superior liner for a Superior heavy liner, I have fitted a Ultra grip probe carrier and slug probe, I also put in a tungsten hammer, Iit was all running fine @960 to 980 fps then I went out shooting it and it was fine, the following day I hadn't touched anything and it wouldn't group,

I checked it over a chronograph and I was getting about a 220fps spread, I was advised on another forum to replaced the tungsten hammer back to the original one, so I have put the original hammer back in and the original spring, but it hasn't made any difference.

Thank you for replying to me.

 

[MongooseV8]

Its the tungsten hammer. You only want to use that in a super maxed out setup. You are waaaay over hammered otherwise which causes erratic fps spreads.

For reference my Impact is 150Bar on the final (only, MK2) reg and I have the Huma hammer spring and a slightly heavier hammer weight. And I still have more room to increase the hammer system. Im shooting a variety of 25 cal slug weights at or around 1000fps.

 

[cwcarrera]

Something that is super easy to check and sometimes overlooked is the 'barrel inlet' O ring. Item # 1 in the link below is the barrel inlet O ring (or breech O ring) and it is subject to wear and failure. Leave the magazine out of your gun and cock it, drape a couple squares of toilet paper over the area where the magazine would live and fire the gun in a safe direction. If it blows the toilet paper off, the O ring is faulty. All of the air should exit the end of the barrel and none should be expelled into the magazine area. Good luck.

https://fxairguns.com/wp-content/uploads/2021/04/F10373-pipkit-impact.pdf

 

[Kevgun]

Its the tungsten hammer. You only want to use that in a super maxed out setup. You are waaaay over hammered otherwise which causes erratic fps spreads.

For reference my Impact is 150Bar on the final (only, MK2) reg and I have the Huma hammer spring and a slightly heavier hammer weight. And I still have more room to increase the hammer system. Im shooting a variety of 25 cal slug weights at or around 1000fps.

Thank you, that has been suggested to me and I have swapped it back for the original setup.

 

[Kevgun]

Something that is super easy to check and sometimes overlooked is the 'barrel inlet' O ring. Item # 1 in the link below is the barrel inlet O ring (or breech O ring) and it is subject to wear and failure. Leave the magazine out of your gun and cock it, drape a couple squares of toilet paper over the area where the magazine would live and fire the gun in a safe direction. If it blows the toilet paper off, the O ring is faulty. All of the air should exit the end of the barrel and none should be expelled into the magazine area. Good luck.

https://fxairguns.com/wp-content/uploads/2021/04/F10373-pipkit-impact.pdf

Thank you I had that fault about 2 week after having the Rifle, and I got a loud pop when firing, I will check it again though, thank you for your suggestion.

 

[Airgunmann]

Its the tungsten hammer. You only want to use that in a super maxed out setup. You are waaaay over hammered otherwise which causes erratic fps spreads.

For reference my Impact is 150Bar on the final (only, MK2) reg and I have the Huma hammer spring and a slightly heavier hammer weight. And I still have more room to increase the hammer system. Im shooting a variety of 25 cal slug weights at or around 1000fps.

The huma spring is heavier spring I'm running standard spring with tungsten hammer at 155 to 160 bar with 56 gr pellets at 920 fps in 30 cal

 

[Airgunmann]

I'd check the end of the hammer make sure the plastic isn't flattened out and also see if c1 moved or is loose

 

[MongooseV8]

The huma spring is heavier spring I'm running standard spring with tungsten hammer at 155 to 160 bar with 56 gr pellets at 920 fps in 30 cal

Yes the Huma spring is heavier, thats why I mentioned my Impact has one. It has been my experience and many others that the tungsten is best in setups using over 150Bar on the final reg. If I wanted to use a high pressure Huma reg at like 170Bar+ with a front reg delete Id throw in the tungsten. And my rifle has proven (at least to me) that for most people a little more hammer than stock is all you really need for ~150Bar. My hammer spring preload is at about 85% from maxed out and the Huma kit includes 2 weights, so I might be able to hit ~160Bar without the tungsten.

 

[Bigragu]

Thank you I had that fault about 2 week after having the Rifle, and I got a loud pop when firing, I will check it again though, thank you for your suggestion.

What have you done to address that pop? I’ve had that happen to me twice, and each time it called for complete disassembly of the valve rod to replace the 2mm x 1mm o ring at the rearmost end of the rod, where it seals at the rear block.

On your valve return spring, factory or aftermarket?

 

[weevil]

Tungsten + 130 bar = trouble. Just to be clear, you’re seeing this variation not just with first few shots but deeper in a string when any oring stiction has passed? If so, I’d say you’ve beat up the valve and it’s best to have FX do the heart surgery. The C1 on the M3 is quite a bit more robust than it used to be.

 

[Airgunmann]

I've cheated and took off the rear lower stock pieces and the gauge block 4 bolts removed the barrel cock the rifle then twist the block to the side and are able slide the rear block off to get at the valve I did this to port the valve and block

 

[IanB]

Hes already stated he has re-installed the original hammer weight and is still having issues...

I also have an M3 and I can relate to the inconsistency and spurious wild spread on a random shot...which led me to delete the 1st stage regulator, although I'm still having issues... my Mk2 are solid totally and no issues... the next thing I'm going to check with the M3 is to remove the new style valve stop adjuster and re-fit a Mk2 adjuster as IMO they are a better design and more consistent... The M3 valve adjuster is a bad design, you have to have it at an invisible line 5 for full power and if you take it near line 2 the gun just will not fire, great engineering !!

There is something amiss with the M3 vs the Mk2 models for sure...

 

[MikeAllen]

Something that is super easy to check and sometimes overlooked is the 'barrel inlet' O ring. Item # 1 in the link below is the barrel inlet O ring (or breech O ring) and it is subject to wear and failure. Leave the magazine out of your gun and cock it, drape a couple squares of toilet paper over the area where the magazine would live and fire the gun in a safe direction. If it blows the toilet paper off, the O ring is faulty. All of the air should exit the end of the barrel and none should be expelled into the magazine area. Good luck.

https://fxairguns.com/wp-content/uploads/2021/04/F10373-pipkit-impact.pdf

Yep - that'll certainly do it! Happened to me and a quick o-ring replacement solved the problem.

 

[Kevgun]

********* UPDATE FIXED **********


Hi, Guys thank you for all your help, I went back over the Rifle, and indeed the breech seal had some damage, I discounted it because i'd only replaced a couple of weeks before, the first one blasted out because the bolt doesn't lock up when closing so if you point the rifle in the air, then the bolt comes back slightly and allowed the pellet probe to expose the breech seal and blasted it out.

my other issue was the C1 (C52) on the M3 wasn't adjusted correctly, I found a youtube video explaining the procedure, the best setting for the M3 is 6.00mm Mine was at 6.6mm so lots of hammer adjustment, but low fps, adjusted it to exactly 6mm and I can run it up 1000fps with 34gr H&N slugs with a 130 bar on the 2nd reg.


Thanks again for all your help, I can get on and use it now.

 

[IanB]

********* UPDATE FIXED **********


Hi, Guys thank you for all your help, I went back over the Rifle, and indeed the breech seal had some damage, I discounted it because i'd only replaced a couple of weeks before, the first one blasted out because the bolt doesn't lock up when closing so if you point the rifle in the air, then the bolt comes back slightly and allowed the pellet probe to expose the breech seal and blasted it out.

my other issue was the C1 (C52) on the M3 wasn't adjusted correctly, I found a youtube video explaining the procedure, the best setting for the M3 is 6.00mm Mine was at 6.6mm so lots of hammer adjustment, but low fps, adjusted it to exactly 6mm and I can run it up 1000fps with 34gr H&N slugs with a 130 bar on the 2nd reg.


Thanks again for all your help, I can get on and use it now.

Alright Kev, you could of just wound the valve stop out further to allow more travel.. just a quicker way than adjusting the hammer seat...

Good to have a few breech seals handy too, has your FPS spread resolved itself now.. ?

 

[Kevgun]

Hi Ian, it is much better, i was getting almost a 300fps spread, it's down to about 20 now, so I need to tinker a bit more, maybe raise the reg pressure a bit more then control it with the valve adjuster, I'm still learning about it. If it was a Rapid 7 i'd have it tuned in 10 minutes

 

[JoePolanco]

Nothing you're experiencing is unusual given the circumstances. This IS an FX gun afterall, not exactly famous for their durability. Although Ive owned a number of FX guns over the years, I currently own 3 highend air rifles, a Daystate Redwolf HP .22, a Skout Epoch in .30, and an FX M3 in .25. Of the 3 the FX is the most complex, least durable and by far the least dependable. Please don't misunderstand, I'm not "hating on" FX, I'm simply stating a fact. Comparisons in this case are not on an "apples to apples" basis, since two of these guns are electronic and the FX is the lone fully mechanical machine. Regardless, one buys the M3 because of it's flexibility, tuneability and accuracy, but not it's durability. The M3, like most of FX's guns, lack a robust design. It's many moving parts, operate under very tight tolerances and since the guns are not robustly designed, these parts wear dramatically over relatively short periods of time. Constant maintenence is a must for virtually any air rifle, however with an FX product, the frequency of repair is double or even tripled of many others. These guns are made of lightweight materials that simply don't stand up to normal use very well or for long without a great deal of attention. In your case, my first thought is that you've broken the hammer spring. This is common issue which frequently shows up as exactly the symptoms you've described. Other possibilities are a bent the catch pin on the cocking lever, a chewed up hammer whose defects are scraping against the walls of its chamber, a cracked or even broken valve or perhaps a loose or misaligned probe, or damaged or missing orings. The list of possibilities is pretty daunting. The bottom line line is, if youre going to shoot pcp airguns, there's a high probability that you're going to have to learn to work on them. Where FX guns are concerned, that "probability" is more of a certainty. The M3 is a great platform but it remains an FX.

 

[Kevgun]

Nothing you're experiencing is unusual given the circumstances. This IS an FX gun afterall, not exactly famous for their durability. Although Ive owned a number of FX guns over the years, I currently own 3 highend air rifles, a Daystate Redwolf HP .22, a Skout Epoch in .30, and an FX M3 in .25. Of the 3 the FX is the most complex, least durable and by far the least dependable. Please don't misunderstand, I'm not "hating on" FX, I'm simply stating a fact. Comparisons in this case are not on an "apples to apples" basis, since two of these guns are electronic and the FX is the lone fully mechanical machine. Regardless, one buys the M3 because of it's flexibility, tuneability and accuracy, but not it's durability. The M3, like most of FX's guns, lack a robust design. It's many moving parts, operate under very tight tolerances and since the guns are not robustly designed, these parts wear dramatically over relatively short periods of time. Constant maintenence is a must for virtually any air rifle, however with an FX product, the frequency of repair is double or even tripled of many others. These guns are made of lightweight materials that simply don't stand up to normal use very well or for long without a great deal of attention. In your case, my first thought is that you've broken the hammer spring. This is common issue which frequently shows up as exactly the symptoms you've described. Other possibilities are a bent the catch pin on the cocking lever, a chewed up hammer whose defects are scraping against the walls of its chamber, a cracked or even broken valve or perhaps a loose or misaligned probe, or damaged or missing orings. The list of possibilities is pretty daunting. The bottom line line is, if youre going to shoot pcp airguns, there's a high probability that you're going to have to learn to work on them. Where FX guns are concerned, that "probability" is more of a certainty. The M3 is a great platform but it remains an FX.

Thank you for your reply, I have fixed my problem, I have been working on PCP Air rifles for a while, but only On Rapid 7 which need the odd O ring every 5 years or so and yes the Impact is complex and very fragile in my opinion, the barrel design being the worst design on the rifle,but the cocking lever is a close second.
I have completely stripped it, inspected and rebuilt and polished off the rough edges, It has been a steep learning curve and sometimes you just need a few pointers from people who have suffered the same pains.

I have fitted a Airmarksman long backbone rail and designed and fitted a barrel band that bolts to the backbone rail, this amongst a few other barrel mods have completely eliminated the zero shift issue I had, Unfortunately the type of Hunting/pest control I do doesn't allow me to carry a Bench and re-zero the rifle, I need it to work straight out of the case.

I have also done a slight mod to the cocking lever that has a small magnet in a brass holder this attaches to the link bar so then closing the bolt it stays home, and doesn't drop back when point the muzzle towards the sky.

It now seems to work okay so far, but, It'll never be a Theoben Rapid in terms of reliability.