Ghost Ultra valve regulator creep

[Corvid_Hunter]

Does the Ultra Valve in the BRK Ghost suffer from reg creep? If so, what is the expectation with regard to first shot POI being off?

 

[ctshooter]

Just my take but I don't see any way in which you can relate a valve to reg creep. Two completely different parts of the rifle. If you have reg creep look at the regulator as the issue. The valve is just a door to let out air.

 

[Franklink]

Depending on how it is set up to produce the desired projectile at the desired speed, yes, the first shot can be slow.

Valve versus regulator is a bit of a chicken or the egg in this case. When I was chasing this down I rebuilt the reg and replaced the reg gauge to rule out reg creep as the cause of slow "cold* shots.

The valve contains a valve stem pocket, opposite the end tapped by the hammer. Some call that pocket the atmospheric chamber. Anywho, there is an oring on the valve stem in that atmospheric chamber that seems to acquire some "stiction" when the gun sits. That oring adherence to the valve stem CAN create a low fps "cold" shot situation.

The oring can be lubed with PTFE containing lubes, which is considered by some to help with the problem. But that does require pulling the valve from the gun.

I've personally found the slow first shot situation is exacerbated by running the gun at modest power levels via light hammer strikes, either from lighter hammer or a lighter hammer spring or lighter hammer spring tension .The opposite holds true as well, heavier hammer strikes minimize the problem of slow fps on "cold" shots.

Since the Ghost can be tuned to produce the same fpe in various ways, my recommendation is to find a combination of settings (reg/hammer spring/hammer spring tension) that produces desired fps from desired projectile with more, rather than less, hammer strike.

 

[Danman]

I am a Ghost newbie but have taken (my .22HP) it out on 3 or 4 sit down sessions so far. First shot is right up there hanging with the rest of the group, zero poi change, but yes the gun is only 2 weeks old. I get the odd flier but I'm shooting Mrds mostly. I do play with the hammer wheel a bit but have been shooting the MRDs currently left on HW 15, now I'm gonna test this with the chrono next time if I can! Are you having an issue with yours Corvid Hunter?

 

[Corvid_Hunter]

I am a Ghost newbie but have taken (my .22HP) it out on 3 or 4 sit down sessions so far. First shot is right up there hanging with the rest of the group, zero poi change, but yes the gun is only 2 weeks old. I get the odd flier but I'm shooting Mrds mostly. I do play with the hammer wheel a bit but have been shooting the MRDs currently left on HW 15, now I'm gonna test this with the chrono next time if I can! Are you having an issue with yours Corvid Hunter?

No issues that I know of. I've only put 3 mags through it so far. I will be getting a hammer spring kit and will try some tuning using Frank's recommendations.

 

[Danman]

The gun likes to be ripped on, and likes its air. With this high a reg pressure shot count is not great. I read ALL of Franklinks reviews and at first alot of guys were perturbed by the high reg pressure and lowering theirs to 90 to 120 bar, thinking they knew better. But then u got the dreaded cold first shot and other issues. Want a low power gun buy one, the ghost is not it. I bought mine to rain doom on paper, cans, and pests 40 to 100 Yards. Get the spring kit, keep reg past 120 and reap all the intended benefits of this sweet gun...and keep us up to date!

 

[KodiakJac]

...my recommendation is to find a combination of settings (reg/hammer spring/hammer spring tension) that produces desired fps from desired projectile with more, rather than less, hammer strike.

Could you please expand on this a bit? I'm at those crossroads right now. I've just joined the N50 Benchrest League and I'm trying to squeeze as much accuracy as I can out of my .22 Ghost HP at 50 yards. I'm shooting MRDs right now. I know, I'm starting to think MRDs and accuracy are an oxymoron...lol

It came from the factory with the reg at 145 BAR, and I was getting really good accuracy shooting the MRD at 960 fps with the PW at 15 (1/2" groups at 50 yards, not including the frustrating MRD flyers). Above 960 it wasn't doing as well, so to get more room at the bottom of my PW to experiment with the 22g JTS, etc. I dropped my reg to about 137 BAR to get 960 fps with the PW on Max.

And that's where I'm at right now. And I feel like I was getting a little better accuracy with the reg at 145 and the PW at 15. But we're talking a gnat's hair better. And with the ever-changing wind variable included, maybe it's just in my mind...lol

Why do you like more hammer strike? 1/2" at 50 yards can feel like a mile when you've got 1 shot at a tiny bullseye.

Thanks!

 

[Franklink]

Could you please expand on this a bit? I'm at those crossroads right now. I've just joined the N50 Benchrest League and I'm trying to squeeze as much accuracy as I can out of my .22 Ghost HP at 50 yards. I'm shooting MRDs right now. I know, I'm starting to think MRDs and accuracy are an oxymoron...lol

It came from the factory with the reg at 145 BAR, and I was getting really good accuracy shooting the MRD at 960 fps with the PW at 15 (1/2" groups at 50 yards, not including the frustrating MRD flyers). Above 960 it wasn't doing as well, so to get more room at the bottom of my PW to experiment with the 22g JTS, etc. I dropped my reg to about 137 BAR to get 960 fps with the PW on Max.

And that's where I'm at right now. And I feel like I was getting a little better accuracy with the reg at 145 and the PW at 15. But we're talking a gnat's hair better. And with the ever-changing wind variable included, maybe it's just in my mind...lol

Why do you like more hammer strike? 1/2" at 50 yards can feel like a mile when you've got 1 shot at a tiny bullseye.

Thanks!

First off, don't let knowledge of this ruin your confidence in your gun. Because of being 50+ fpe I doubt it'll be a problem for you.

The low fps first shot problem seems to mostly be a problem for compromise tunes. In my case, I was using the same reg pressure/hammer/hammer spring for 3 different projectiles and 3 different desired speeds by utilizing the power wheel (hammer spring tension). The reg pressure was technically too high for the lowest fpe tune. So using MIN on the wheel for that tune meant the first couple "cold" shots were low fps.

I personally think it has to do with valve stem travel. By knocking the valve stem harder (through any combination of heavier hammer, heavier hammer spring, or more hammer spring tension) it travels more, more easily breaking free from that oring stiction. With tiny little light taps of the valve stem (again via the hammer when the trigger is pulled), I think it takes a couple of them to break that oring free from where it's wanting to stick on the valve stem. Once it's broken free, fps will be right where you had it last time you were shooting. In my experience, a heavy hammer hit makes it more quickly lose that "memory" of conforming to the same spot on the valve stem.

For best results in competition, configure the gun specifically for that projectile at that fps. if you can do so with more, rather than less, hammer strike, you are likely to not deal with any low fps "cold" shots.

You are talking about a 25.4grain pellet going 960. That'll be roughly 52fpe. And 52 fpe will require a pretty decent hammer strike. With that power output I doubt you'll see the oring stiction on the valve stem issues that I'm describing above.

Finally, to rule out low fps on initial shots, shoot the gun over the chronograph when cold. Do this a couple times, letting the gun sit for a day or more between each time so that the shots truly are "cold" shots. You'll know real quick if your first shots are slightly slower than the rest or not.

And finally finally, benchrest lets you have as many sighters as you want. Even if you do have slow cold shots, burn off a few at the beginning of a card and then you're in business. Slow initial shots are a bigger problem in disciplines where you don't get sighters, like field target or shooting pests.

 

[Corvid_Hunter]

The shooting pests with a slow first shot is my main concern.

 

[Franklink]

The shooting pests with a slow first shot is my main concern.

Relatively high reg pressure allows more fps variation from the power wheel. But also tends to create low fps "cold" shots in the "Min" end of the wheel.

Using the reg to limit the fpe output usually equates to no slow fps cold shots. (ie use a reg pressure only high enough to produce the desired fps from the desired projectile). But this also means more hammer tension via the wheel doesn't increase the fps.

So, decide if you prioritize being able to spin the power wheel to get more fps (and likely have low fps cold shots on the MIN end of the wheel). Or if you prioritize being able to use the first shot out of a gun that's been sitting for awhile. If you like trustable first shots, dial the reg pressure back down to juuusssttt high enough to produce the fpe you're after, and leave it there.

 

[Danman]

Relatively high reg pressure allows more fps variation from the power wheel. But also tends to create low fps "cold" shots in the "Min" end of the wheel.

Using the reg to limit the fpe output usually equates to no slow fps cold shots. (ie use a reg pressure only high enough to produce the desired fps from the desired projectile). But this also means more hammer tension via the wheel doesn't increase the fps.

So, decide if you prioritize being able to spin the power wheel to get more fps (and likely have low fps cold shots on the MIN end of the wheel). Or if you prioritize being able to use the first shot out of a gun that's been sitting for awhile. If you like trustable first shots, dial the reg pressure back down to juuusssttt high enough to produce the fpe you're after, and leave it there.

So Franklink in a hunting/competition situation like he is describing, if you have been shooting the gun @ say HW setting 1 the day or two before and wanted to blast something quick, or just haven't taken a shot prior to remedy the issue, you could just dial the wheel to say 15 and that should be enough to smack the valve and break the sticking o-ring free? (Of course you have to know what it does poi on that setting @ whatever distance) Thanks.

 

[Franklink]

So Franklink in a hunting/competition situation like he is describing, if you have been shooting the gun @ say HW setting 1 the day or two before and wanted to blast something quick, or just haven't taken a shot prior to remedy the issue, you could just dial the wheel to say 15 and that should be enough to smack the valve and break the sticking o-ring free? (Of course you have to know what it does poi on that setting @ whatever distance) Thanks.

Maybe.

Hammer setting one from the prior day may not even have the slow cold shot situation, depending on how the gun is tuned.

The ultimate concept to understand here is that the regulator pressure is constantly pushing against the valve stem, sealing it to the valves face. "Firing" the gun is slightly opening that seal, for a split second. Dwell and lift are two of the terms often used here. Dwell is how long the valve is open and lift is how much it opens ("valve stem travel" was the phrase I used in the earlier posts). Dwell and lift are controlled by the amount and type of energy imparted on the valve stem by the hammer strike. Shot cycles and efficiency of a PCP can be optimized through tweaking of dwell and lift. Wildcatters in the PCP world that are making their own valves and other parts get real crazy with this valve and lift concept. For the Ghost in OEM form, as the tweaking of these factors is limited to the amount of energy we strike the valve with. And the amount of energy is through the hammer spring and or hammer spring tension.

The regulator pressure and amount of valve strike is a delicate balance, because those are the two opposing forces we're playing with, all of it revolving around that very small area of interface between those forces at the sealing junction of the valve stem and valve face.

So, a reg pressure that is relatively high (read "too high") for a given fpe output means that you don't need to strike the valve very hard to get that fpe. In the case if my 20fpe .20 tune, that meant a reg pressure of 128bar and "MIN" on the power wheel produced 805fps with 13.73grain pellets. With more hammer tension but same reg pressure I can get up to 34fpe from the same barrel and heavier projectiles. Because I could get that much fpe from the same reg pressure we know that that reg pressure is too high for the sub20fpe tune. So in order for that reg pressure to put out only 20fpe, were depending on a light hammer strike. That light hammer strike means the valve stem is hardly moving when struck ("lift"). That means the stem isn't traveling much inside that oring in the atmospheric chamber, and the minimal travel means it takes a couple shots for it to break free from the stiction and then move freely. Those couple shots have low fps.

In contrast, if the intent was a sub 20fpe tune, running with a reg down around 90-105 bar would mean the valve needs hit harder to open more to let "more" of that lower pressure air "out" to propel the pellet. That heavier hammer strike means the valve stem travels more, meaning it breaks free from the stiction easier, ie, no slow fps on "cold" shots.

The sub12fpe Ghosts in the UK sound like they have reg pressures in the 105-110 bar range, per the Ghost Facebook group. The .177 barrels have a small transfer port, which is another factor in all this. A small transfer port is another way to "strangle" power down and increase efficiency. By limiting the "exit" when the valve is open, "less" air is released from each hammer strike.

Lots going on when we pull the trigger, thinking through the balancing acts of all those opposing forces helps a guy arrive at the "best" tune for what they're wanting to do.

Lots of Chrono work is the best way to understand all of this, and to truly know your personal Ghost and how it behaves in various scenarios, dependant on how you've chosen to "tune" it.

 

[Corvid_Hunter]

Relatively high reg pressure allows more fps variation from the power wheel. But also tends to create low fps "cold" shots in the "Min" end of the wheel.

Using the reg to limit the fpe output usually equates to no slow fps cold shots. (ie use a reg pressure only high enough to produce the desired fps from the desired projectile). But this also means more hammer tension via the wheel doesn't increase the fps.

So, decide if you prioritize being able to spin the power wheel to get more fps (and likely have low fps cold shots on the MIN end of the wheel). Or if you prioritize being able to use the first shot out of a gun that's been sitting for awhile. If you like trustable first shots, dial the reg pressure back down to juuusssttt high enough to produce the fpe you're after, and leave it there.

Thanks for your detailed explanations. I ordered a spring kit from Brocock which should be here in a week or so. If I'm understanding this correctly, I should find the best fps for 33.49gr JSBs and then reduce my regulator pressure and go to a lighter spring where I end up with the power wheel on or near Max for the desired fps?

 

[Franklink]

Thanks for your detailed explanations. I ordered a spring kit from Brocock which should be here in a week or so. If I'm understanding this correctly, I should find the best fps for 33.49gr JSBs and then reduce my regulator pressure and go to a lighter spring where I end up with the power wheel on or near Max for the desired fps?

You may be perfectly fine with the 33.49gr JSBs with whatever spring came in the gun.

The slow fps on cold shots that I've dealt with has been at 19fpe. A 33.49grain pellet tells me you're not looking for 19fpe.

Once you arrive at the settings that you like for accuracy/fpe, let the gun sit for a full day (or more) and then run cold shots over the chronograph to see what you've got.

When I was running the Ghost as a 50fpe .22, the fps of the first shot out of the gates was right where it was supposed to be.

And when I was running it as a 19fpe .177, with an appropriate reg pressure, the first (cold) shots were also spot on.

The slow fps on cold shots occurrence is a symptom of a reg pressure that is high enough for lots more power and using really light hammer spring tension to reign it in.

An appropriate reg pressure usually means the hammer wheel doesn't do much for fps variation. I've seen SOOO many new Ghost owners in the last 18 months complaining that the wheel doesnt change the fps. That's cuz that reg pressure is probably perfect for what you're trying to do. So as I said yesterday, decide if you want the power wheel to do much (usually accomplished by too high of reg pressure) or if you want reliability with one projectile at one desired speed (achieved by an appropriate reg pressure, and usually a mid range setting on the power wheel).

 

[Danman]

You may be perfectly fine with the 33.49gr JSBs with whatever spring came in the gun.

The slow fps on cold shots that I've dealt with has been at 19fpe. A 33.49grain pellet tells me you're not looking for 19fpe.

Once you arrive at the settings that you like for accuracy/fpe, let the gun sit for a full day (or more) and then run cold shots over the chronograph to see what you've got.

When I was running the Ghost as a 50fpe .22, the fps of the first shot out of the gates was right where it was supposed to be.

And when I was running it as a 19fpe .177, with an appropriate reg pressure, the first (cold) shots were also spot on.

The slow fps on cold shots occurrence is a symptom of a reg pressure that is high enough for lots more power and using really light hammer spring tension to reign it in.

An appropriate reg pressure usually means the hammer wheel doesn't do much for fps variation. I've seen SOOO many new Ghost owners in the last 18 months complaining that the wheel doesnt change the fps. That's cuz that reg pressure is probably perfect for what you're trying to do. So as I said yesterday, decide if you want the power wheel to do much (usually accomplished by too high of reg pressure) or if you want reliability with one projectile at one desired speed (achieved by an appropriate reg pressure, and usually a mid range setting on the power wheel).

Could not agree more sir. I get 100fps difference on average with the reg @165. That's perfect for fine tuning. For shot count and simplicity sake I may drop it to 150bar some day. I think they set up the gun right, and then it's up to the owner what to do, if anything from there. MRDS MIN to MAX 890 TO 990. And 18.1 - 995 TO 1092. She's a bit hot! Got a ton of 19, 21, 23gr stuff to try soon

 

[Corvid_Hunter]

You may be perfectly fine with the 33.49gr JSBs with whatever spring came in the gun.

The slow fps on cold shots that I've dealt with has been at 19fpe. A 33.49grain pellet tells me you're not looking for 19fpe.

Once you arrive at the settings that you like for accuracy/fpe, let the gun sit for a full day (or more) and then run cold shots over the chronograph to see what you've got.

When I was running the Ghost as a 50fpe .22, the fps of the first shot out of the gates was right where it was supposed to be.

And when I was running it as a 19fpe .177, with an appropriate reg pressure, the first (cold) shots were also spot on.

The slow fps on cold shots occurrence is a symptom of a reg pressure that is high enough for lots more power and using really light hammer spring tension to reign it in.

An appropriate reg pressure usually means the hammer wheel doesn't do much for fps variation. I've seen SOOO many new Ghost owners in the last 18 months complaining that the wheel doesnt change the fps. That's cuz that reg pressure is probably perfect for what you're trying to do. So as I said yesterday, decide if you want the power wheel to do much (usually accomplished by too high of reg pressure) or if you want reliability with one projectile at one desired speed (achieved by an appropriate reg pressure, and usually a mid range setting on the power wheel).

Once again, thanks. I have my Crown MK2 .25cal with a 380mm barrel set up shooting the 25gr JSBs at around 650fps for closer range pests and plinking. The crows and magpies seem to have a comfort zone of around 90-100 yards. These I hope to introduce to the Ghost. I'll also be target shooting at the same distances so I'm just going to use the 33gr JSBs until I decide on getting a slug barrel or not.

 

[KodiakJac]

First off, don't let knowledge of this ruin your confidence in your gun. Because of being 50+ fpe I doubt it'll be a problem for you.

The low fps first shot problem seems to mostly be a problem for compromise tunes. In my case, I was using the same reg pressure/hammer/hammer spring for 3 different projectiles and 3 different desired speeds by utilizing the power wheel (hammer spring tension). The reg pressure was technically too high for the lowest fpe tune. So using MIN on the wheel for that tune meant the first couple "cold" shots were low fps.

I personally think it has to do with valve stem travel. By knocking the valve stem harder (through any combination of heavier hammer, heavier hammer spring, or more hammer spring tension) it travels more, more easily breaking free from that oring stiction. With tiny little light taps of the valve stem (again via the hammer when the trigger is pulled), I think it takes a couple of them to break that oring free from where it's wanting to stick on the valve stem. Once it's broken free, fps will be right where you had it last time you were shooting. In my experience, a heavy hammer hit makes it more quickly lose that "memory" of conforming to the same spot on the valve stem.

For best results in competition, configure the gun specifically for that projectile at that fps. if you can do so with more, rather than less, hammer strike, you are likely to not deal with any low fps "cold" shots.

You are talking about a 25.4grain pellet going 960. That'll be roughly 52fpe. And 52 fpe will require a pretty decent hammer strike. With that power output I doubt you'll see the oring stiction on the valve stem issues that I'm describing above.

Finally, to rule out low fps on initial shots, shoot the gun over the chronograph when cold. Do this a couple times, letting the gun sit for a day or more between each time so that the shots truly are "cold" shots. You'll know real quick if your first shots are slightly slower than the rest or not.

And finally finally, benchrest lets you have as many sighters as you want. Even if you do have slow cold shots, burn off a few at the beginning of a card and then you're in business. Slow initial shots are a bigger problem in disciplines where you don't get sighters, like field target or shooting pests.

Thanks for this, Franklink!

It has helped me better understand what's going on inside airguns.

Cheers!