Regulator suddenly at 170, from 140 bar?

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kmd1984

Member
Feb 20, 2016
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Utah, United States
Hi,

What can cause a regulator to go from 140 to 170 bar...?

Spring is around the corner so I decided to "re-zero" my Bobcat Mk2. I took it out back and started shooting at 25 meters. As always, the gun puts pellet after pellet in the same hole. This was done on high power. I then decided to zero the scope at low power as well. I have a MTC Viper so having multiple zeros is not an issue.

Here is the "weird" part: Upon switching to lower power, my pellets did not just drop, but they also went to the right?! The first shot, after switching to the lower power setting, always went farther right than the following ones?! I would say about an inch at 25 meters, whereas following shots would be off by maybe half an inch. I would like to also point out that once I was shooting at lower power for a few shots, the groups, although to the right, were pretty tight. Not as tight as on full power though. Once I switched to high power again, the pellets would be "centered" again.

This whole thing really "threw" me off, as the gun never did this before. Sure, lower power would always make the pellet drop, but NEVER make it go off center?!

After shooting for a little bit, the "first pellet way off center" issue was suddenly gone??? The pellets would still be off center a little bit, but the groups got way tighter, and no more flyer at the beginning.

So, that is when I realized that my regulator pressure is set at 170 and not at 140, as it always has been?! I have no clue why my regulator suddenly went up.

That said.

1. What can cause a regulator to just change?
2. Since when does lowering power make pellets go off center? Especially when my gun has never done this before.
3. Why does the issue seem to be gone once the tank and regulator have equal pressure?


Thanks,

Kmd
 
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Here's my thought.

1) When the regulator seat gets pounded from regulating it will eventually get a "groove" in it. This groove will allow additional air to enter (basically leaking) after the regulator reaches it's set pressure. The additional air entering causes the pressure to be higher then the set pressure. This is "creep". You can usually replace this seal (on aftermarket units) and all is usually good. With my stock FX wildcat regulator it doesn't look like it's a replaceable part, so I ordered a Huma. Not sure on the Bobcat. I can say the regulator in my WC does not seem to be built near as well as the Audrius, Lane or Huma's I have used in the past.
2) I would think it's just the change in the velocity of the pellets. Some pellets, if sped up, or slowed down don't just go faster or slower, their flight changes. Hence why some pellets fly best at a specific speed range. I'm guessing it would also be caused by scope/gun cant if you are not using a level.
3) As the tank pressure drops the pressure on the regulator seat decreases and does not allow as much air to "leak" past the seal.
 
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 ​BigTinBoat,

1) I know too little about air rifles, but I can see how "creep", caused by "wear and tear", could be the cause of this. I have around 5000 pellets through this gun and never ever had a single issue, so I guess it was about time that something goes kaputt?! : )
At this point, I am not sure if I should replace the o-rings/seals on the existing regulator or go for the Huma one?! I guess it all depends on how "complicated" and time consuming "fixing" the FX regulator is. 

2) Hmmm? Let me think... I have tested different pellets with this gun myself, and I have to agree. Some pellets work better than others. No doubt.
If I remember correctly, brand A might be flying more to the right than brand B. However, I only saw a shift in POI along the horizontal axes when changing brand, not when changing the power setting. In other words: I would zero my scope with JSB's. Once zeroed, the pellet would pretty much always land dead center. When I now switched the power level from high to low, the pellet (Brand A), would not change along the horizontal axes, but only along the vertical one. Now. If I take a different pellet altogether (Brand B), I might get a change in POI along the horizontal axes as well [compared to Brand A). But again. No change in POI with Am I explaining it right? : )

3). OK.

Thanks for the input!

Kmd
 
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My gun did the same thing. If you set reg pressure above 150 then you run the risk of damaging the Delron reg piston. I never turned the reg pressure down while pressurized but low and behold, it was damaged. I bought a new one and now I keep pressure at 120-125 bar for .25. Also try replacing reg piston o-ring and the two small o-rings on the reg adjust screw. Might try that first, might get lucky. 
 
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"kmd1984"
​BigTinBoat,
1) I know too little about air rifles, but I can see how "creep", caused by "wear and tear", could be the cause of this. I have around 5000 pellets through this gun and never ever had a single issue, so I guess it was about time that something goes kaputt?! : )
At this point, I am not sure if I should replace the o-rings/seals on the existing regulator or go for the Huma one?! I guess it all depends on how "complicated" and time consuming "fixing" the FX regulator is. 
2) Hmmm? Let me think... I have tested different pellets with this gun myself, and I have to agree. Some pellets work better than others. No doubt.
If I remember correctly, brand A might be flying more to the right than brand B. However, I only saw a shift in POI along the horizontal axes when changing brand, not when changing the power setting. In other words: I would zero my scope with JSB's. Once zeroed, the pellet would pretty much always land dead center. When I now switched the power level from high to low, the pellet (Brand A), would not change along the horizontal axes, but only along the vertical one. Now. If I take a different pellet altogether (Brand B), I might get a change in POI along the horizontal axes as well [compared to Brand A). But again. No change in POI with Am I explaining it right? : )
3). OK.
Thanks for the input!
Kmd

Click to expand...
I would think it's the piston seal causing the problem. I tried to "re-surface" the one in my WC, but I'm still getting the variances. I honestly don't like the design of the FX reg. I bit the bullet and got a Huma from Trenier.
 
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"AirGunShooter"I just had a very similar thing happen just yesterday to a new Huna regulator installed in a .25 Marauder. The reg was set at 135 bar and after approximately 500 rounds, the set pressure jumped up to 160 bar and stayed there for over 100 more rounds. Finally I took the reg out and checked to make sure the adjuster had somehow not changed. It had not. So I twisted the adjuster back and forth over a small range and again set it to 135 bar. Back in the rifle again and now it is holding. All very weird, especially after having so many rounds through it. I have installed, tested and used MANY Huma regs, plus I have shot tens-of-thousands of rounds through FX regulated rifles and never to my knowledge experienced a pressure change such as this.
Click to expand...
Interesting. Thanks for sharing.

Kmd
 
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"Drumsnguns"My gun did the same thing. If you set reg pressure above 150 then you run the risk of damaging the Deleon reg piston. I never turned the reg pressure down while pressurized but low and behold, it was damaged. I bought a new one and now I keep pressure at 120-125 bar for .25. Also try replacing reg piston o-ring and the two small o-rings on the reg adjust screw. Might try that first, might get lucky.
Click to expand...
Thanks for the info...

My next step is to find out which (is it which or what? Anyhow...) is "easier", to replace the seals or to replace the whole regulator?! If I had to take an educated guess, I would think that it is a give or take.
If you plan on replacing the seals only, you have to take out the regulator anyway. Once you take it out, you might as well screw a new one in? Right? 
I replaced many seals on many items, so I do not see an issue with that. 

That said. How do I take the regulator out? I found this video, but there are a few things that are not clear to me. One of them is; do I have to degas the same way he does? I would think not, but I am not sure. At around 01:30 he says that the tube does not have a "check valve". From my understanding, my Bobcat Mk2 does. So does that mean I can just unscrew the tank, cock the gun, fire it and it will be degassed? If that is the case, I would hope that after there is no more gas in it, there is no danger of getting hurt anymore?!

Thanks for all the input!

Kmd

p.s. I only found a place in Europe to sell a Huma reg for the Bobcat Mk2. If anyone knows of any other place, please share that info with me. : )
 
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You can order direct from Huma, it'll only take about two weeks to get it. For the Bobcat MK2, you can unscrew the pressure tube with it pressurized. Sometimes the reg will allow the rest of the pressure to bleed off (you can tell by the reg pressure gage), sometimes it doesn't. If it doesn't a few shots will get the pressure to zero. There is also a brass screw near the reg pressure gage that you can CAREFULLY unscrew to bleed off pressure... The reg is very simple to remove and replace. Unscrew the piece that the tube screws into. Under that piece is the reg. Reach in with needle nose pliars and remove it (if I remember correctly, you may need an M3 metric screw to screw into the top of the reg, makes it easier to pull it out). MEASURE the total length of the reg and write it down before proceeding. Then disassemble, clean everything really well, replace the software (orings) and reassemble with light coating of silicon grease. Make sure when you reassemble you adjust to the same length as before you took it apart. Or, just buy a Huma and insert it in place of the stock reg. When you install the Huma, the brass adjuster screw goes UP, not down, which appears to be the opposite of the stock FX reg you removed. Easy...
 
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"You can order direct from Huma, it’ll only take about two weeks to get it."
I get stuff from Europe all the time... two weeks sounds about right.

"For the Bobcat MK2, you can unscrew the pressure tube with it pressurized. Sometimes the reg will allow the rest of the pressure to bleed off (you can tell by the reg pressure gage), sometimes it doesn’t. If it doesn’t a few shots will get the pressure to zero."
Ahh. Now that you mention it... I have taken the air tube off before and remember seeing the reg gauge being at Zero. 

"There is also a brass screw near the reg pressure gauge that you can CAREFULLY unscrew to bleed off pressure…"
Just to confirm. Is this an and/or scenario? I believe it to be more of an "or", as in "You can either remove the air tank and bleed the air off, OR you unscrew the brass screw and bleed the air off that way. Correct? 

"The reg is very simple to remove and replace. Unscrew the piece that the tube screws into. Under that piece is the reg. Reach in with needle nose pliars and remove it (if I remember correctly, you may need an M3 metric screw to screw into the top of the reg, makes it easier to pull it out)."
Roger that. 

"MEASURE the total length of the reg and write it down before proceeding. Then disassemble, clean everything really well, replace the software (orings) and reassemble with light coating of silicon grease. "
So far, so good. : )

"Make sure when you reassemble you adjust to the same length as before you took it apart."
I make sure of that! 

"Or, just buy a Huma and insert it in place of the stock reg. When you install the Huma, the brass adjuster screw goes UP, not down, which appears to be the opposite of the stock FX reg you removed. Easy…"
If I find one in the US, I will probably end up buying it. Not sure what you mean by, "the brass adjuster screw goes UP, not down..." I guess and hope it will make more sense once I remove the regulator. 

Thank you so much for the detailed description... One more thing. Which way do I have to screw/adjust the reg if I want to lower the pressure? No matter what I end up doing, I have to do something. TODAY, ha ha. If I do not at least try to change the reg pressure before I replace it, it will haunt me for ever. That is just how I am. I need to know. I need to know if it was a "fluke" or if something was actually wrong with it!

Thank again everyone for the great help!

Kmd
 
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OK, here you go.

Yes, its an "or" scenario for the brass screw

​Where I say "up", that was for the Huma. For the FX reg., the Belleville stack goes down into the cavity the same as it comes out...

​If you want to LOWER the pressure, turn it so that the Belleville Washers are less compressed, which I think is counter clockwise. These adjustments are VERY SMALL. This is not like adjusting the HST on your gun. Just a small amount, about 1/16 of a turn, certainly no more than 1/8, but I'd say closer to 1/16 turn will probably give you 10 bar...
​Mike
 
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OK, here you go.
3 - 2 - 1 - GO! : )

Yes, its an “or” scenario for the brass screw
Roger that.

 Where I say “up”, that was for the Huma. For the FX reg., the Belleville stack goes down into the cavity the same as it comes out…
I see. Makes sense.

​If you want to LOWER the pressure, turn it so that the Belleville Washers are less compressed, which I think is counter clockwise. These adjustments are VERY SMALL. This is not like adjusting the HST on your gun. Just a small amount, about 1/16 of a turn, certainly no more than 1/8, but I’d say closer to 1/16 turn will probably give you 10 bar…
Mike, you are Magic! (Sorry, I am sure you hear that a lot...)

Thanks again!

Kmd
 
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OK, as expected, I am "stuck"...

I took the air tank off. No problem. However, the pressure did not go down all the way. I then tried the brass screw, but it didn't do anything. I was able to unscrew it all the way but nothing. The pressure did not go down. Firing a few shots doesn't really do that much. I would have to fire a bunch to make the pressure go all the way to zero. I am not sure if that is a good idea though?! I read somewhere that "dry-firing" is not good for PCP guns. Maybe this is not really considered dry-firing because the pressure is low???

Thanks,

Kmd
 
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Kmd. That’s odd about the gun not degassing. With my gun you unscrew the bottle. Uncock it and set the power wheel to MIN. Then shoot it. It should hiss out the through the bottle mount. If not try it again. Do not dry fire to empty. Once the pressure drops below 100bar, you run the risk of damaging the valve. If it’s not degassing then something is wrong. 
Check the reg gauge if it’s close to zero you can loosen the reg gauge and it will drain to zero. 

If you tear in to the reg u might as well take it all apart. Not much extra work. 
If you have time polish the reg piston with 3M polishing paper. Also polish the Belleville washers too. I did and it tightened up the extreme spread. If problems keep asking questions. 
 
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"Drumsnguns"Kmd. That’s odd about the gun not degassing. With my gun you unscrew the bottle. Uncock it and set the power wheel to MIN. Then shoot it. It should hiss out the through the bottle mount. If not try it again. Do not dry fire to empty. Once the pressure drops below 100bar, you run the risk of damaging the valve. If it’s not degassing then something is wrong. 
Check the reg gauge if it’s close to zero you can loosen the reg gauge and it will drain to zero. 
If you tear in to the reg u might as well take it all apart. Not much extra work. 
If you have time polish the reg piston with 3M polishing paper. Also polish the Belleville washers too. I did and it tightened up the extreme spread. If problems keep asking questions.
Click to expand...
Thanks for the input! I might have actually figured it out!– I took the air tank off. Gauge still showing around 30 bar or so.
– I then "dry fired" the gun a few times. YES, I know. You are not supposed to do that. Anyhow. If I remember correctly, that didn’t really drop the pressure either, which is really weird, if you think about it.
– I then loosened the brass screw. Nothing. Pressure did not move! WTF???
– I then used an Allen wrench through the HST adjuster (or whatever it is called?!). Again. NOTHING. The pressure is NOT going down???

That is when a light went off, and I started to realize what was going on...

– Lastly, I unscrewed the gauge. The gauge was still showing 30 bar?!Wait a minute. What is going on?! How can the gauge STILL show any pressure? I guess the only plausible answer to that is that the gauge is defective?! Right?After a few moments of being speechless it dawned on me! Two or three weeks ago, I ”dropped” my rifle. It was more of a ”it slipped out of my hand” thing, instead of a real drop. Anyhow. Fact is that it landed on its butt! Like I said, the drop didn’t feel hard at all. But who knows?! Maybe that is all it took to ”off-set” the gauge?!If you look at how the gauge is mounted, you can clearly see how a ”hit” would make the needle move towards a higher reading…Sounds like the regulator is fine and that it is just the needle that ”moved” and is now showing a wrong reading.
That would also explain why my muzzle velocity didn’t change, and it should right? Going from 140 to 170 should increase the fps, or not?Anyhow. I really believe I figured it out?!Thanks,Kmd
 
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Good news. If it was keeping you ES respectable before you disassembled it I would leave the reg alone and just put it back together with a new reg pressure gage. My reg pressure gage reads accurately but the tube pressure gage was off by at least 20 bar. I replaced it with a Wika gage, so now both gages read within 5 bar once I get to or below reg pressure. I have an EDgun EDMU that I plan on installing once I ream out the end and of the dustcover 1.6mm. 
 
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