Read this whole thread and I have made myself the peek spacer washer. Will report back. I’m using the NBR 90 oring not the PUR 90 oring. I also used 400 grit sand paper for the valve rod.
Last edited:
Upvote 0
Tuning FX Impact Mk2/M3 - slower first shot - no reg creep - quasi-scientific analysis
- Thread starter Seeker
- Start date
That's what I did to my 720/power block up grade to my PP M2. I got the 100 fps back I lost when I upgraded (?). I came real close to reinstalling the original PP as the first shot was slow but after that no problem. Ya know, Fx could make our lives much better if they just would instead of making it tapered make it flat like the peek washer accomplishes. Yes, instead of just buying standard drill bits to drill the passage they'd have to maybe use a long 4 flute end mill.
Upvote 0
For whatever I am shooting I tune mine to peak performance at PW 13. Them when the gun has set long periods I turn it up to 15 or 16 for the first few shots. Not perfect by any means but it does help greatly. 2k plus gun really shouldn’t do this.
Upvote 0
I still think most of it can be tuned out or to at least a acceptable level where it really doesn't change point of impact
Just my honest opinion
Just my honest opinion
Upvote 0
I just registered on this site to give Seeker and Vetmx a huge thank you! By chasing this issue to ground and giving me the confidence to make/use the peek washer/ viton75 o-ring you both fixed what was otherwise a $2200 mistake.
A quick FYI, I got my brand new M3 in May 2024 and it had a black o-ring instead of the white one shown in previous posts. I have no way of knowing if it was NBR or PUR from the factory, but I'm guessing it was NBR. If it was NBR, this may have been an attempt by FX to fix this issue, but without a peek washer it was still giving the low FPS for the first 5-10 shots. Short story long, I don't think just dropping a NBR90 o-ring in there will solve the problem for those tempted to do so.
My results with with peek washer and viton 75 o-ring were a 1st ten shot string with e.s. of less than 6fps. This was after sitting for 18 hours. The factory setup would drop 20-40 fps if I took a 1 hour lunch break!
A quick FYI, I got my brand new M3 in May 2024 and it had a black o-ring instead of the white one shown in previous posts. I have no way of knowing if it was NBR or PUR from the factory, but I'm guessing it was NBR. If it was NBR, this may have been an attempt by FX to fix this issue, but without a peek washer it was still giving the low FPS for the first 5-10 shots. Short story long, I don't think just dropping a NBR90 o-ring in there will solve the problem for those tempted to do so.
My results with with peek washer and viton 75 o-ring were a 1st ten shot string with e.s. of less than 6fps. This was after sitting for 18 hours. The factory setup would drop 20-40 fps if I took a 1 hour lunch break!
Upvote 0
Looks like I spoke too soon. Left the gun at 250bar and ~ 40 hours later it was down to 110bar. Probably due to my machining of the washer, but either way the washer is out and the viton o ring is in w/o a backer of any kind. I'll report back with results of a '24 hour later' 10 shot string. If the results are decent I'm going to consider the viton o ring a high replacement item and leave it. mcmaster sells 50 of them for about $4, so I'm not breaking the bank if I have to change it once a year.
Upvote 0
What you describe is characteristic of many air rifles. After sitting, it takes 3-5 shots for them to loosen up. Just shoot the first ones in the dirt. Even rimfire rifles have a cold shot problem. Don't worry about it.
Upvote 0
22 hours later and no leaks. 1st shot was 40fps slow. Shots 2-10 were all within 7fps of each other. I think I can live with 1 shot dump. The 6-8 shots required with the stock o ring weren't cutting it though.
Upvote 0
I did some further testing to determine when (or if) the viton 75 oring with no washer would cause issues. The setup is stock internals except the viton oring and a slight polish on the valve rod where the oring rides. A bit of Super Lube in that area. .25 700mm slug barrel with 1:16t 1st reg 155, 2nd reg 145, valve adjuster at ~ 4.5 lines with stock spring and no rubber balls. Micro maxed and then it moves to whatever correlates to Macro on 13. H&N 42 grain .249 slugs that average 910fps when it is warmed up.
So it looks like I'll do two dump shots to be safe and can sit waiting for at least 2 hours without major issues.
| time inactive | 1st shot | 2nd shot | 3rd shot |
| 22 hrs | 879 -31fps | 887 -23 | 911 +1 |
| 2 hrs | 889 -21 | 909 -1 | 909 -1 |
| 1 hr | 891 -19 | 888 -22 | 910 |
| 20 min | 900 -10 | 906 -4 | 910 |
| 18 min | 898 -12 | 911 +1 | 899 -11 |
Upvote 0
Put the FKM 90 oring in. First shot was about 20fps slower. Second and subsequent shots were pretty much spot on. Consistency seems ok. Will need to do more testing. Previously with NBR 90 oring I was still getting second and third shot lower fps.
PS: I am using the peek washer mod aswell.
PS: I am using the peek washer mod aswell.
Upvote 0
I guess now the question will be longevity.... I'll update if I develop a leak. Please do the same.
Upvote 0
UPDATE: no leaks with FKM 90. First shot is still low fps But second and subsequent shots are spot on.
I watched a YouTube video by Ernest Rowe on the M4 and I found his response to a comment interesting about the valve rod plenum seal.
Someone from here commented on his YouTube video about the peek spacer.
I watched a YouTube video by Ernest Rowe on the M4 and I found his response to a comment interesting about the valve rod plenum seal.
Someone from here commented on his YouTube video about the peek spacer.
Upvote 0
Reg creep is inevitable, mitigation is the key.
We're talking molecules that are at average .3 nano meters in size....
1mm = 1,000,000 nano meters.
Or .3 nano meters = 0.0000003mm
Which means your regulator seat to piston and their entire geometry which mate together must not be outside of 0.0000002mm to completely remove regulator creep...
Outside of tuning hot, and over driving the valve while using a 'stop' much like impacts do with their lift limiter to mitigate it, the next best solution is minimizing the effects caused by regulator creep, which would be with valve technology, be it an electronic valve that can detect the small variations in pressure and adjust lift/dwell accordingly, or a valve that has a lower pressure differential given the same % of reg creep, such as severely reducing the force holding the valve shut. If at 140 bar your valve has 140 lbs holding it shut, and at 150 bar 150 lbs, that is a huge 10 lb swing in pressure, where as a valve with 28 lbs holding it shut at 140 bar and 30 lbs at 150 bar, that is only a 2 lb swing, which is far less to mitigate even though its the same % change in pressure...
The more overall force holding the valve shut, the more regulator creep will express itself regardless of any valve/hammer balance. Go to an extreme, and a valve with 14,000 lbs of force holding it shut at 140 bar, and 15,000 at 150 bar...well, hopefully by now you get the point, the further we go the further the valve/hammer harmony will become...well unbalanced, as regulator creep presents itself...
-Matt
We're talking molecules that are at average .3 nano meters in size....
1mm = 1,000,000 nano meters.
Or .3 nano meters = 0.0000003mm
Which means your regulator seat to piston and their entire geometry which mate together must not be outside of 0.0000002mm to completely remove regulator creep...
Outside of tuning hot, and over driving the valve while using a 'stop' much like impacts do with their lift limiter to mitigate it, the next best solution is minimizing the effects caused by regulator creep, which would be with valve technology, be it an electronic valve that can detect the small variations in pressure and adjust lift/dwell accordingly, or a valve that has a lower pressure differential given the same % of reg creep, such as severely reducing the force holding the valve shut. If at 140 bar your valve has 140 lbs holding it shut, and at 150 bar 150 lbs, that is a huge 10 lb swing in pressure, where as a valve with 28 lbs holding it shut at 140 bar and 30 lbs at 150 bar, that is only a 2 lb swing, which is far less to mitigate even though its the same % change in pressure...
The more overall force holding the valve shut, the more regulator creep will express itself regardless of any valve/hammer balance. Go to an extreme, and a valve with 14,000 lbs of force holding it shut at 140 bar, and 15,000 at 150 bar...well, hopefully by now you get the point, the further we go the further the valve/hammer harmony will become...well unbalanced, as regulator creep presents itself...
-Matt
Upvote 0