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

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The O-ring design from Accu-Shot doesn’t really make sense. If it sits in a conical seat, it will eventually clamp down on the rod over time. You can use almost any material you like.

The only logical solution is to use an O-ring that sits flat and is secured in place either by a locknut, or with something like FX’s approach using a Delrin insert. Hency why they drilled the surface flat in the new plenum necks.

Why worry about refresh rate? I dont get it. I run a Huma regulator in my Impact, and mine refreshes under one second. I mostly shoot Benchrest with a single-shot tray, so it’s never been an issue.
 
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PcpMachinist said:
re inventing the wheel, the new plenum is fine once installed in the gun strength wise its clamped in, it also takes the same o ring as the DRS Leopard and Panthera
the guys over at accu shot orings had these made roughly 4-6 weeks ago .
Click to expand...

I fixed my DRS Slow shot. Polish the valvepin and install a NBR 90 oring instead of PUR. Solved.

FX - FX DRS Slow Shot - Solved

Hi Folks, I’ve been working for a while on solving the slow first shot issue in the FX DRS. I’ve done various tests and tried different types of O-rings and greases. Finally, after working on it for a long time, I can say that I’ve pretty much solved the problem, as long as the DRS is properly...
www.airgunnation.com www.airgunnation.com
 
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Ries said:
The O-ring design from Accu-Shot doesn’t really make sense. If it sits in a conical seat, it will eventually clamp down on the rod over time. You can use almost any material you like.

The only logical solution is to use an O-ring that sits flat and is secured in place either by a locknut, or with something like FX’s approach using a Delrin insert. Hency why they drilled the surface flat in the new plenum necks.

Why worry about refresh rate? I dont get it. I run a Huma regulator in my Impact, and mine refreshes under one second. I mostly shoot Benchrest with a single-shot tray, so it’s never been an issue.
Click to expand...
yes it does and they work ,you can get as technical as you would like, I've been to there shop , i have seen the 1000s of o rings Etc. have you seen or tested there plenum o ring ? or how its designed or shape or are you just assuming? all 4 of my impacts have them and im very happy with the purchase es and sd of all 4. anyhow this issue has been cured imo. watch this video there is plenty of them with the same results
 
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PcpMachinist said:
yes it does and they work ,you can get as technical as you would like, I've been to there shop , i have seen the 1000s of o rings Etc. have you seen or tested there plenum o ring ? or how its designed or shape or are you just assuming? all 4 of my impacts have them and im very happy with the purchase es and sd of all 4. anyhow this issue has been cured imo. watch this video there is plenty of them with the same results
Click to expand...

I have tested alot before I purchased a plenum neck, I know what im talking about.

Why did FX change the part design now and milled the surface flat instead of conical? Because any oring under pressure will clamp overtime on the rod. The conical shape and pressure is the is main issue. The older impacts pre powerplenum all had the locknut to hold the oring.

I have Mubhaur his part and even informed FX sereval times about the problem. People who got the new plenumneck from FX or Mubhaur dont have the slow shot anymore, all without a “special compound” oring.



Watch at 5:26 , he shows the first slow shot there even with the “special” orings in it. Hmm sure its working..
 
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As Ries already pointed out, there is no type of o-ring that can solve this issue in the plenum part with a conical seat.
FX has been aware of this problem from the very beginning, but they don’t want it to cost them.
That’s why they once changed the type of o-ring in the M4, but since the problem still persists, they are now forced to modify the part.
Which they continue to do in the cheapest way possible by modifying an existing part.

In reality, an o-ring is never the right type of seal for axial movement. This was mentioned earlier in the topic as well.
Still, in this application it worked well enough: in the first Impacts, in Mubhaur’s modified part, and now again in FX’s revised part.

A new o-ring will always provide some improvement at first, because there is fresh lubrication and the ring has not yet taken the shape of the conical seat. However, I would strongly advise against disassembling your Impact just to replace the o-ring, only to find out later that the problem still hasn’t been solved.
 
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Apollo said:
As Ries already pointed out, there is no type of o-ring that can solve this issue in the plenum part with a conical seat.
FX has been aware of this problem from the very beginning, but they don’t want it to cost them.
That’s why they once changed the type of o-ring in the M4, but since the problem still persists, they are now forced to modify the part.
Which they continue to do in the cheapest way possible by modifying an existing part.

In reality, an o-ring is never the right type of seal for axial movement. This was mentioned earlier in the topic as well.
Still, in this application it worked well enough: in the first Impacts, in Mubhaur’s modified part, and now again in FX’s revised part.

A new o-ring will always provide some improvement at first, because there is fresh lubrication and the ring has not yet taken the shape of the conical seat. However, I would strongly advise against disassembling your Impact just to replace the o-ring, only to find out later that the problem still hasn’t been solved.
Click to expand...

So from what im understanding, correct me if im wrong. You need Mubhaurs part to fix? If i find a smoking deal on a used Impact thats the first upgrade ill do. I do not want to support FX directly.
 
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CrashKT said:
So from what im understanding, correct me if im wrong. You need Mubhaurs part to fix? If i find a smoking deal on a used Impact thats the first upgrade ill do. I do not want to support FX directly.
Click to expand...
Not only this thread, but please also check this one.
FX has recently made some changes to the plenum end, and it looks like using it helps improve the situation.

FX - FX IMPACT - NEW VALVE ROD.

Greetings Mubaur It is my understanding that you offered the part design to FX and they refused . If so can you say why they refused . Thanks Mubaur As I remember I offered it to Huma-Air without any payment. They refused saying, "We are familiar with this mod but it is not an item what...
www.airgunnation.com www.airgunnation.com
 
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The big advantage of the Mubhaur part is that the o-ring is easy to replace compared to the FX part, because they press a plastic bush behind it.
This bush is only there to support the o-ring during installation. I didn't use it and instead just used a supporting o-ring like before, which works just as well.
The o-ring seat of the FX part is also way more thinner, which should be sufficient, but the Mubhaur part is much sturdier there.

The new valve rod will help, but it is not necessary to solve the problem. After a week sitting idle with the new plenum part and the old valve rod:

1758351512108.png
 
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i have had both plenums mubhars and the accu shot oring plenum they both do the same job period
the new plenum from fx uses the smaller drs leopard valve pin o ring and has has issues. Gen one works better with 2 o rings .
and yes the Accu -Shot o rings fix this slow shot issue its that simple ok i also know what I'm talking about and not going to
bother get your data correct because you obviously never tried or seen there o rings
so your just ASSUMING VS FACTS and the FACT is THEY WORK.
keep re inventing the wheel good luck ACCU-SHOT ORINGS FIXED THIS PROBLEM A YEAR AGO get over your theory and put the facts on paper
all i know is all 4 of my impacts have no more cold shot issue they can sit for a day or week 1st shot is 5-8fps off 2nd on is right on
GO ARGUE THAT.. get another covid shot..
 
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You can achieve a small spread with any Impact.
As the title of this topic indicates, it concerns the first slow shot after a period of inactivity.

I don't care what people buy or don't buy, I just want to give them all the information I have.

This topic contains all the dimensions, modifications, and o-ring types used in the updated FX plenum part.
It includes also sufficient explanation to understand why they modified it and even measured data.

All information is available to the forum members and anyone who wants to can even customize it themselves based on that.

It would be credible if you could provide us with more information about the Accu shot o-ring.
Maybe by saying what type of o-ring this is, or do they have them custom-made for them in terms of type and material composition?

In that case they are are only available through them of course, but still very cheap because they probably have them made by the thousands.

@FX, the conical seat was not a design flaw after all.
It was simply that no suitable o-ring had been developed and made for it yet. Until now that is.
So stop wasting your time and money modifying or redesigning the plenum part and just buy the Accu shot o-ring from the factory.
You can thank PcpMachinist for the tip.
 
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PcpMachinist said:
i have had both plenums mubhars and the accu shot oring plenum they both do the same job period
the new plenum from fx uses the smaller drs leopard valve pin o ring and has has issues. Gen one works better with 2 o rings .
and yes the Accu -Shot o rings fix this slow shot issue its that simple ok i also know what I'm talking about and not going to
bother get your data correct because you obviously never tried or seen there o rings
so your just ASSUMING VS FACTS and the FACT is THEY WORK.
keep re inventing the wheel good luck ACCU-SHOT ORINGS FIXED THIS PROBLEM A YEAR AGO get over your theory and put the facts on paper
all i know is all 4 of my impacts have no more cold shot issue they can sit for a day or week 1st shot is 5-8fps off 2nd on is right on
GO ARGUE THAT.. get another covid shot..
Click to expand...
Dear
I admit that I didn't use Accu Shot O ring. If you say that it fixed the issue, I am more than happy as Impact users might have got a cost effective solution.

To be fair, I am not in this business. I am just a hobbiest. Find very little time to do all this. I try to find out solutions to the PCPs which are in my use. Where I find issues, I even go to the extend to see if the wheel had correctly been invented initially. That is how I work in my profession as I am a professional accountant and a Liquidator of a Public Limited company these days.

If I find a solution to a problem, through whatever means, I adopt it. When I see a lot of users facing similar issues, I try to help them out at very thin profit margins. If I include my time, I do it rather at a loss.

I am not a mechanical engineer nor doing it as business.

The users of FX Impact and RAW who have got my developed parts so far give me positive feedback.

I am a bit old school. However, if someone comes up with an easy solution I am more than happy, rather I might try it in my guns at some point.

I am not in love afair with my solutions.

It appears that you do not know me or do not understand me.

However, I am very happy if users found an easy fix.

Have a good day and let me reinvent the wheel. The wheels might be improved at some stage.

Mubhaur
 
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PcpMachinist said:
i have had both plenums mubhars and the accu shot oring plenum they both do the same job period
the new plenum from fx uses the smaller drs leopard valve pin o ring and has has issues. Gen one works better with 2 o rings .
and yes the Accu -Shot o rings fix this slow shot issue its that simple ok i also know what I'm talking about and not going to
bother get your data correct because you obviously never tried or seen there o rings
so your just ASSUMING VS FACTS and the FACT is THEY WORK.
keep re inventing the wheel good luck ACCU-SHOT ORINGS FIXED THIS PROBLEM A YEAR AGO get over your theory and put the facts on paper
all i know is all 4 of my impacts have no more cold shot issue they can sit for a day or week 1st shot is 5-8fps off 2nd on is right on
GO ARGUE THAT.. get another covid shot..
Click to expand...

Why so mad? Im not assuming, I know what im talking about.

An oring that sits in a conical seat will clamp the rod. I dont care about the orings, its not something magical. If FX changed the design, there is a reason.
Its not my fault you dont understand the whole problem, read this whole thread again.

Now calm down and enjoy the Impact.
 
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I can tell you that I have installed the 'special' O-Rings in my M2. I STILL must fire at a minimum of 9 shots for the velocity to come up to the setting. This with polishing the rod.
Starting at 813 and growing in increments of around 10-15FPS until reaching 925FPS.
Do the magical O-Rings work for me? Nope!

mike
 
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I dont know which variable did it, but my 1st shot being unacceptably low (where poi was a deal breaker) ended when I did dual huma regs and a tungsten hammer weight. Maybe I'm just brute forcing that valve open every time and stopping it with the va, or have taken some ridiculous amounts of data and tried high pressure and low pressure to find where it behaves best.
 
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mubhaur said:
Dear
I admit that I didn't use Accu Shot O ring. If you say that it fixed the issue, I am more than happy as Impact users might have got a cost effective solution.

To be fair, I am not in this business. I am just a hobbiest. Find very little time to do all this. I try to find out solutions to the PCPs which are in my use. Where I find issues, I even go to the extend to see if the wheel had correctly been invented initially. That is how I work in my profession as I am a professional accountant and a Liquidator of a Public Limited company these days.

If I find a solution to a problem, through whatever means, I adopt it. When I see a lot of users facing similar issues, I try to help them out at very thin profit margins. If I include my time, I do it rather at a loss.

I am not a mechanical engineer nor doing it as business.

The users of FX Impact and RAW who have got my developed parts so far give me positive feedback.

I am a bit old school. However, if someone comes up with an easy solution I am more than happy, rather I might try it in my guns at some point.

I am not in love afair with my solutions.

It appears that you do not know me or do not understand me.

However, I am very happy if users found an easy fix.

Have a good day and let me reinvent the wheel. The wheels might be improved at some stage.

Mubhaur
Click to expand...
we are all in it for the hobby some of shoot bench rest some hunt some plinkers
i have owned Fx air guns since they were produced.
i have seen all the changes and band aids
and yes this is an old subject that was fixed over a year ago and it seem some on this site just know everything.
thats fine then you should have no issues with your guns because you know .

that's great been a machinist for 53 years in jet propulsion .
and very old school
Revoman said:
I can tell you that I have installed the 'special' O-Rings in my M2. I STILL must fire at a minimum of 9 shots for the velocity to come up to the setting. This with polishing the rod.
Starting at 813 and growing in increments of around 10-15FPS until reaching 925FPS.
Do the magical O-Rings work for me? Nope!

mike
Click to expand...

Ries said:
Why so mad? Im not assuming, I know what im talking about.

An oring that sits in a conical seat will clamp the rod. I dont care about the orings, its not something magical. If FX changed the design, there is a reason.
Its not my fault you dont understand the whole problem, read this whole thread again.

Now calm down and enjoy the Impact.
Click to expand...
im not mad and fact is none of my guns have an issue with this slow shot problem so it sounds to me
like you have not found your issue, its not just the o rings..
have you ever seen what an o ring does under extreme pressure in a conical seat?
you may want to take a look of do some reading up on it..
 
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