Brocock/BRK Ghost regulator not holding set point

[greenbeans]

So I put a digital gauge on my ghost a few days ago to confirm a suspicion I had about the reg… Turns out the suspicion was justified. I usually had the reg at 140ish but since I had to degas anyway to put the gauge on it o lowered a bit to work my way up. At 250b bottle pressure, the reg is sitting at 124b. When shooting the bottle down, the following happens with the reg set point (I gave it 45 seconds refresh time between all shots):

- 123b reg at 235b bottle
- 122b reg at 220b bottle
- 121b reg at 205b bottle
- 120b reg at 190b bottle
- 119b reg at 175b bottle
- 118b reg at 165b bottle
- 117b reg at 155b bottle
- 116b reg at 145b bottle

I didn’t shoot it further down yet to let it sit at 145b to see how fast it creeps back up over a couple of hours. Now I get it that this is to some extent expected but assuming the reg will end up at like 114-115b with the bottle at 130b, that’s almost 10b of lost plenum pressure down from 250b… plus it’s almost a linear decline in set point, 1b every 15b bottle pressure or so.

Before I tear into it and look at the reg, anybody experienced something similar and has an idea what can be done about it other than polish and rebuild the reg? The reg was adjusted maybe 4-5 times from new over a year or so that I have it, of course never down under pressure.

Thanks in advance!!

 

[nervoustrig]

Dressing the seat surfaces is indeed the way to improve it. It's actually not that bad, though, A decline from 124 bar down to 114 bar is a change of about 8%. Anything under 10% is usually rendered inconsequential if the gun is adjusted for the velocity knee. Has the gun been difficult to coax into producing a stable velocity?

 

[greenbeans]

Dressing the seat surfaces is indeed the way to improve it. It's actually not that bad, though, A decline from 124 bar down to 114 bar is a change of about 8%. Anything under 10% is usually rendered inconsequential if the gun is adjusted for the velocity knee. Has the gun been difficult to coax into producing a stable velocity?

That’s helpful, thanks!!! On most of the others I have it it’s way less, though most of them have polished reg internals. Just never had a reason to pull the reg from the ghost yet and only polish them while I have them out for other reasons

Yeah makes sense as to tuned to the knee, though when going with lighter ammo and using the power wheel to go down it’s noticeable cause you’re sometimes 10-15% below the plateau…

 

[cavedweller]

So I put a digital gauge on my ghost a few days ago to confirm a suspicion I had about the reg… Turns out the suspicion was justified. I usually had the reg at 140ish but since I had to degas anyway to put the gauge on it o lowered a bit to work my way up. At 250b bottle pressure, the reg is sitting at 124b. When shooting the bottle down, the following happens with the reg set point (I gave it 45 seconds refresh time between all shots):

- 223b reg at 235b bottle
- 222b reg at 220b bottle
- 221b reg at 205b bottle
- 220b reg at 190b bottle
- 119b reg at 175b bottle
- 118b reg at 165b bottle
- 117b reg at 155b bottle
- 116b reg at 145b bottle

I didn’t shoot it further down yet to let it sit at 145b to see how fast it creeps back up over a couple of hours. Now I get it that this is to some extent expected but assuming the reg will end up at like 114-115b with the bottle at 130b, that’s almost 10b of lost plenum pressure down from 250b… plus it’s almost a linear decline in set point, 1b every 15b bottle pressure or so.

Before I tear into it and look at the reg, anybody experienced something similar and has an idea what can be done about it other than polish and rebuild the reg? The reg was adjusted maybe 4-5 times from new over a year or so that I have it, of course never down under pressure.

Thanks in advance!!

I’ll bet there is some debris or metal edging that’s nicked your orings

 

[greenbeans]

I’ll bet there is some debris or metal edging that’s nicked your orings

Thanks! Gonna pull the reg one of these days and take a look, will report back!

 

[Trucker3573]

Don’t agree that it isn’t bad. The reg should never start at 223 bar and def shouldn’t stay over 200 bar for 4 shots. Rebuild time. Mine on my DW slowly creeps down across the shot count. Ends up losing like 10 bar across the whole shot string. I like a dummy turned twice the wrong way under pressure. Pretty sure I damaged the little delrin disk in the reg. Been waiting for a long time for A of A to get the huma reg rebuild kits back in stock. Refuse to pay shipping from Huma. Wait wait wait.

 

[greenbeans]

Don’t agree that it isn’t bad. The reg should never start at 223 bar and def shouldn’t stay over 200 bar for 4 shots. Rebuild time. Mine on my DW slowly creeps down across the shot count. Ends up losing like 10 bar across the whole shot string. I like a dummy turned twice the wrong way under pressure. Pretty sure I damaged the little delrin disk in the reg. Been waiting for a long time for A of A to get the huma reg rebuild kits back in stock. Refuse to pay shipping from Huma. Wait wait wait.

Ha! You got me and I messed up the numbers, corrected them above…

 

[Trucker3573]

Ha! You got me and I messed up the numbers, corrected them above…

Ok…lol. Yeah yours isn’t bad. Kind of does what mine is doing. However mine didn’t do that before so it does bug me and I know I accidentally adjusted it in under pressure so I must change it. As far as I know the only way to get the little delrin piece is buying the reg rebuild kit.

 

[greenbeans]

Ok…lol. Yeah yours isn’t bad. Kind of does what mine is doing. However mine didn’t do that before so it does bug me and I know I accidentally adjusted it in under pressure so I must change it. As far as I know the only way to get the little delrin piece is buying the reg rebuild kit.

Yeah it bugs me as well… 50% as a matter of principle, the other 50% because you can really see it in the string when using the power wheel to dial it down for lighter ammo…

 

[greenbeans]

Well, I pulled the reg and everything looked good, except for two things (that I saw):

Piston and Belleville washers were dripping in lube, literally wet as if they were simply dumped in a jar of thin lube…

Second, it seems the stack is grabbing the housing:

Not sure how this could cause the set point creeping down though…

So in the end nothing obvious and I simply ran it through standard polishing procedure… can’t tell you whether it worked though because the rifle is now leaking air out of the barrel as fast as I can fill it. Used a burst from a tank, cocked while filling etc but air simply rushing through… so the valve’s up next I guess…

 

[greenbeans]

Dressing the seat surfaces is indeed the way to improve it. It's actually not that bad, though, A decline from 124 bar down to 114 bar is a change of about 8%. Anything under 10% is usually rendered inconsequential if the gun is adjusted for the velocity knee. Has the gun been difficult to coax into producing a stable velocity?

Just realized that I never answered your question as to difficulties to produce tight strings. Not at all, it’ll give me ES 5 and SD 1.3 on the power wheel setting that’s giving 97.5% of plateau speed. It’s getting bad once I use the PW to go down quite a bit to shoot lighter ammo though… but I’m probably 20-30% below plateau at that point…