FX Impact STX reg creep

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Paio

Paio

Member
Apr 20, 2015
178
2
Minas Gerais, Brazil
Fellow FX Impact shooters and tuners:

I have been trying to tune my Impact STX .25 (JSB 25.39gr) since I got the gun. I have 900 shoots so far. I maximized the hammer (on max) and slowly increased the reg pressure until pellet velocity no longer increase. VS adjuster is backout (4 bars). My velocity target is 3-5% below the max. I have done several, several attempts but doesn't matter what I do my first shots after gun is idle for hours or the next morning are always way over the ES. Usually much lower speed than the previous one. Some days it takes up to 4 shots and others like 10 until the gun stabilizes within ES normal range.This reg creep is quite annoying for a new gun. It is Gen 3 and I have the new AMP reg. I have always degassed the gun before lower the pressure in spite of supposedly I don't have to do it.

Based upon your experiences:

1 - What am I doing wrong?
2 - Should I try to repair the reg replacing their orings or should I go directly to a Huma reg and forget the stock one? I am kind of tired...

Your thoughts will be appreciated. 
 
Hello, here is a hint

Order is: Reg, HST, Valve ... I read HST, Reg, Valve.

Did you really max your HST for the reg pressure? & did you use a 1.5 mm allen key to adjust the HST screw? (Since you did not mention that I have to ask), if you add more pressure to the reg, you should always get more speed, if you are not getting it, is because the HST is not in max and the hammer is not opening the valve fully. (and is Reg and then HST, in that order)

It might be that...(hopefully) ;) if not you might want to check this: http://www.airgunnation.com/topic/first-shot-lower-fps-on-regulated-pcp/


 
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It's normal I believe. And you aren't the only one. I see a lot of others have the same issue. I also have the Impact x 600mm. My reg is about 140. Few hours to overnight it creep maybe 5-6 bars. But it effect the fps. I tested over my chrony. Heavy 33.95 shooting 850-865 on the reg. But leave for few hour or overnight. It will shoot low 820, then 2nd shot will shoot 830, then back to 850+. I don't think you can do anything about it. I took the reg out, clean it and lub it and it still does the same thing. I suggest upgrade to a huma reg for $90 or just leave it. Don't try to fix it, you could break it even more. If you don't want to upgrade to a huma, just shoot 1-2 shots before you go out hunting or shooting.
 
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I was experiencing the same initial low velocity shots, that would increase after a shot or two as well. I think that the initial low velocity shots are due to the valve rod and hammer and spring portion of the gun needing to "warm up" to being cycled because it needs lubed to be constent, and needing a touch more hammer weight to overcome valve creep. Try cleaning and greasing those portions of the gun and o-rings to see it it helps clear it up. When I cleaned the rod, springs and valve I added about 6 grams of brass hammer weight that which also added 1.5mm of spring preload. I also opened up my valve seat to 6mm and ported the transfer port/pellet probe area so my shot spreads are very consistent now, (gaining 40+ FPS in the process), but because of this my results are skewed as I didn't do just one thing then test, so your results my vary.
 
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Hi,

You have to find the correct balance, this is very difficult if not done methodically/in the correct order. Firstly I feel that your reg is too low for .25 25gr, I would aim for about 128Bar. Then I think that you are over stroking the hammer, look for a distance of about 18mm, leave your valve open. Doing this will bring your gun closer to the default configuration for .25. Definitely have a look at the impact troubleshooting manual, the gun should perform at the default setting to a certain standard, if yours does not when set up at defaults then there may be some other issue that needs to be addressed, like a torn c3 oring, slow leak or leak during the shot cycle.

You need to have a velocity in mind before tuning, around 910 fps is a good starting point, you then need to adjust the hammer until you get to about 920fps. Then start with the valve adjuster, until you get to about 910 FPS. Doing this means that when your reg creeps you have enough hammer to overcome the extra pressure, then when the reg settles down the valve limiter stops the over speeding. If your gun is in tip-top shape you will get about 10fps ES if not then about 20 FPS ES.

If your gauges are the standard type then unfortunately you can't be sure what pressure your reg is actually at, and you are just going to frustrate yourself making adjustments. A low reg pressure and long hammer dwell is wasteful, rather try a slightly higher reg and shorter hammer dwell time, especially for .25

Get orings, leak detector, good tools, silicone grease, mosquito forceps and oring picks, there aren't many issues that cant be sorted if you have the right tools and the troubleshooting manual.
 
Upvote 0
Hello, here is a hint

Order is: Reg, HST, Valve ... I read HST, Reg, Valve.

Did you really max your HST for the reg pressure? & did you use a 1.5 mm allen key to adjust the HST screw? (Since you did not mention that I have to ask), if you add more pressure to the reg, you should always get more speed, if you are not getting it, is because the HST is not in max and the hammer is not opening the valve fully. (and is Reg and then HST, in that order)

It might be that...(hopefully) ;) if not you might want to check this: http://www.airgunnation.com/topic/first-shot-lower-fps-on-regulated-pcp/

Click to expand...

Thanks. When I say the HST was maximized I mean screw the HST slider (1.5mm screw) until there is no play back and forth. Then play with the reg in very small turns until I see the max speed. Thanks for the AGN post. I will read it. 
 
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at 120 bar (1740 psi), a .3" poppet would have 125 lbs of force holding it closed. Once a Regulator creeps to 125.5 bar (1820 psi), there would be 131 lbs of force holding the poppet closed, which is a difference of 5%...so you can expect roughly 5%~ drop in velocity on the first shot compared to when the reg is at its intended pressure.



850 *.05 = 42~ fps, so seeing 810-820 fps on first shot in the above condition would be considered normal and expected. IMO.



-Matt
 
Upvote 0
Hello, here is a hint

Order is: Reg, HST, Valve ... I read HST, Reg, Valve.

Did you really max your HST for the reg pressure? & did you use a 1.5 mm allen key to adjust the HST screw? (Since you did not mention that I have to ask), if you add more pressure to the reg, you should always get more speed, if you are not getting it, is because the HST is not in max and the hammer is not opening the valve fully. (and is Reg and then HST, in that order)

It might be that...(hopefully) ;) if not you might want to check this: http://www.airgunnation.com/topic/first-shot-lower-fps-on-regulated-pcp/

Click to expand...

Thanks. When I say the HST was maximized I mean screw the HST slider (1.5mm screw) until there is no play back and forth. Then play with the reg in very small turns until I see the max speed. Thanks for the AGN post. I will read it.
Click to expand...

That is what you are doing wrong , first reg and then hst, check the link, is Ernest Rowe telling that (sniperlabyo). You do not need to max the HST on 120 bar
 
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hat is what you are doing wrong , first reg and then hst, check the link, is Ernest Rowe telling that (sniperlabyo). You do not need to max the HST on 120 bar

ith the reg in very small turns until I see the max speed. Thanks for the AGN post. I will read it.
Click to expand...

Thanks Edosan.

I read the post on the link and it was educational. I will increase the reg pressure and reduce the HST and see what I can find. 

However, based upon I have read in several posts as well as videos (Ted and Matt) in order to tune properly the Impact we need to find the right balance between reg and HST. Being two variables in this equation if I keep one fixed, I thought I could work on the other one to find that balance. I.e., keep the HST at max and increase the reg pressure until I have the curve knee and fine tuning the valve adjust knob to reduce speed in 5% to be the best combination of harmonics and shot count. 

Well, that is the theory behind. Doing it is not always easy. thanks again.
 
Upvote 0
It's normal I believe. And you aren't the only one. I see a lot of others have the same issue. I also have the Impact x 600mm. My reg is about 140. Few hours to overnight it creep maybe 5-6 bars. But it effect the fps. I tested over my chrony. Heavy 33.95 shooting 850-865 on the reg. But leave for few hour or overnight. It will shoot low 820, then 2nd shot will shoot 830, then back to 850+. I don't think you can do anything about it. I took the reg out, clean it and lub it and it still does the same thing. I suggest upgrade to a huma reg for $90 or just leave it. Don't try to fix it, you could break it even more. If you don't want to upgrade to a huma, just shoot 1-2 shots before you go out hunting or shooting.
Click to expand...

This gonna be my plan B. I will do some tinkering on the stock reg. In spite of I didn't have any success yet, it has been very educational... thanks for your comment.
 
Upvote 0
Hi,

You have to find the correct balance, this is very difficult if not done methodically/in the correct order. Firstly I feel that your reg is too low for .25 25gr, I would aim for about 128Bar. Then I think that you are over stroking the hammer, look for a distance of about 18mm, leave your valve open. Doing this will bring your gun closer to the default configuration for .25. Definitely have a look at the impact troubleshooting manual, the gun should perform at the default setting to a certain standard, if yours does not when set up at defaults then there may be some other issue that needs to be addressed, like a torn c3 oring, slow leak or leak during the shot cycle.

You need to have a velocity in mind before tuning, around 910 fps is a good starting point, you then need to adjust the hammer until you get to about 920fps. Then start with the valve adjuster, until you get to about 910 FPS. Doing this means that when your reg creeps you have enough hammer to overcome the extra pressure, then when the reg settles down the valve limiter stops the over speeding. If your gun is in tip-top shape you will get about 10fps ES if not then about 20 FPS ES.

If your gauges are the standard type then unfortunately you can't be sure what pressure your reg is actually at, and you are just going to frustrate yourself making adjustments. A low reg pressure and long hammer dwell is wasteful, rather try a slightly higher reg and shorter hammer dwell time, especially for .25

Get orings, leak detector, good tools, silicone grease, mosquito forceps and oring picks, there aren't many issues that cant be sorted if you have the right tools and the troubleshooting manual.
Click to expand...

Thanks for your comments. I have stock gauges and agree they are kind of frustrating. I will increase reg pressure and reduce HST. Let's see how this work. I will proceed as well checking the leaks. 
 
Upvote 0
at 120 bar (1740 psi), a .3" poppet would have 125 lbs of force holding it closed. Once a Regulator creeps to 125.5 bar (1820 psi), there would be 131 lbs of force holding the poppet closed, which is a difference of 5%...so you can expect roughly 5%~ drop in velocity on the first shot compared to when the reg is at its intended pressure.



850 *.05 = 42~ fps, so seeing 810-820 fps on first shot in the above condition would be considered normal and expected. IMO.



-Matt
Click to expand...

Thanks Matt. Good info. 
 
Upvote 0
hat is what you are doing wrong , first reg and then hst, check the link, is Ernest Rowe telling that (sniperlabyo). You do not need to max the HST on 120 bar

ith the reg in very small turns until I see the max speed. Thanks for the AGN post. I will read it.
Click to expand...

Thanks Edosan.

I read the post on the link and it was educational. I will increase the reg pressure and reduce the HST and see what I can find. 

However, based upon I have read in several posts as well as videos (Ted and Matt) in order to tune properly the Impact we need to find the right balance between reg and HST. Being two variables in this equation if I keep one fixed, I thought I could work on the other one to find that balance. I.e., keep the HST at max and increase the reg pressure until I have the curve knee and fine tuning the valve adjust knob to reduce speed in 5% to be the best combination of harmonics and shot count. 

Well, that is the theory behind. Doing it is not always easy. thanks again.
Click to expand...

Your thoughts are right! But if I understand correct what ER is saying, first the reg, you need to match the HST to the Reg pressure, no the reg pressure to the HST, since if you do it the way you did, you will have inconsistencies. 

I would remove the air from the gun, decrease the hst to min, attach the bottle again, then un the reg to 120 and then start to increase the hst until there is no more speed increase in the chrony. Then check with the HST wheel in 5-4-3-2-1 that is ok, if 5 is the same or similar or higher than max, the screw is probably too tight.

Let us know if you could find the problem! glad I can help.
 
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"Your thoughts are right! But if I understand correct what ER is saying, first the reg, you need to match the HST to the Reg pressure, no the reg pressure to the HST, since if you do it the way you did, you will have inconsistencies. 

I would remove the air from the gun, decrease the hst to min, attach the bottle again, then un the reg to 120 and then start to increase the hst until there is no more speed increase in the chrony. Then check with the HST wheel in 5-4-3-2-1 that is ok, if 5 is the same or similar or higher than max, the screw is probably too tight."
Click to expand...

Well, this is a quick update on my recent tuning with your instructions above. First shot still low after 24 hours but not as low as before. However, within a 3 hours idle 1st shot is within ES of 1.44% which for hunting is acceptable. Pellets are unsorted and I think I can reduce ES later on. I am attaching two graphs. 1st is how I tuned. 2nd is my shot string after 24 hours. I am happy with the results and I am not sure if I can improve it since I am using stock FX reg. I kept reg at 125BAR (using FX stock gauges). 

Please take a look on it. Also, to others please feel to jump here and add your considerations. 

1553605038_7416859445c9a21ae8e6d21.21221166_FX Impact Graph 1.jpg


1553605778_7943205565c9a2492eb65e6.15378420_FX Impact Graph 2.jpg
 


 
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I am not an expert, but I am not sure the term "knee" is where you have marked it, in your diagram.

If the gun is shooting fine, you have probably not found a bad tune. But it looks to me if you go lower on speed with same regpressure, the gun will probably be more efficient with air, and give more shots.

I personally would test some of the lower speed settings also with same reg pressure, just to see how accuracy compares, while shooting on target. 
 
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@paio it got better? glad to read...

you know what is funny? I just got a negative comment on my profile (accuracy) just for trying to help you... looks like some people care more about egos than solutions.

I am not even English speaking native! , and this guy (the one with the negative comment) is interpreting what I am saying! I really do not care much about it, is just funny. That was very recently.

1553686345_7981671735c9b5f4910a491.15129258_neg.jpg



 
Upvote 0
I am not an expert, but I am not sure the term "knee" is where you have marked it, in your diagram.

If the gun is shooting fine, you have probably not found a bad tune. But it looks to me if you go lower on speed with same regpressure, the gun will probably be more efficient with air, and give more shots.

I personally would test some of the lower speed settings also with same reg pressure, just to see how accuracy compares, while shooting on target.
Click to expand...

I am not an expert either and I am learning all these great airguning stuff. So, answering your points:

The knee, as I think, is where I see the max velocity. After that I don't see too much spread and we call that the plateau. If I continue to increase the HST I would see a downslope curve and then I could see clearly he knee curve. However I reached the max HST in my Impact. Please let me know where you think where the knee is. Please take a look on https://hardairmagazine.com/ham-columns/tuning-regulated-pcp-airguns/ by Bob Sterne. That is where I got my rationale behind my graph. 

I agree that reducing the speed I could see better air efficiency and more shots. I think -5% is the best tuning according to the tuning guys. However I want my Impact for hunting. That's why I kept it with a higher velocity. 

I still need to to check accuracy and see with that tuning the gun is accurate. 

Thanks for your comments.
 
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