Brocock/BRK Ghost reg issue?

[IKnowNutin]

I bought a ghost from the classifieds here a while back and noticed it had a slow leak from the weep hole that could actually be heard if in a really quiet room. I utilized this forum and BRK's excellent maintenance videos to troubleshoot and fix the leak by replacing some O-rings on the regulator. I actually completely disassembled, cleaned and replaced all the O-rings since I had it apart anyway. Pretty easy with all the resources available. Put it back together and had no more leaks, yay! But.......after setting the regulator to 150b and shooting a couple hundred pellets through it I've noticed the first shot of the day was slower and had a different POI than follow on shots for the rest of the session. The tiny Huma reg gauge didn't show a pressure change from what I had set but I began to wonder how accurate it was because something is changing. Put the chrony on it and discovered the 1st shot to be way slower than everything after it. Here's the latest 24 shot string:

Shot count: 24
Low: 807
Hi: 893
Avg: 871
STD Dev: 15
Spread: 86

7/21/24 17:40:44,807,FPS,64.8,FT Lbs,
7/21/24 17:41:01,861,FPS,73.6,FT Lbs,
7/21/24 17:41:20,872,FPS,75.6,FT Lbs,
7/21/24 17:41:37,863,FPS,74.0,FT Lbs,
7/21/24 17:41:52,886,FPS,78.0,FT Lbs,
7/21/24 17:42:05,872,FPS,75.6,FT Lbs,
7/21/24 17:42:18,872,FPS,75.6,FT Lbs,
7/21/24 17:42:35,870,FPS,75.2,FT Lbs,
7/21/24 17:43:18,865,FPS,74.4,FT Lbs,
7/21/24 17:43:26,879,FPS,76.8,FT Lbs,
7/21/24 17:43:34,868,FPS,74.8,FT Lbs,
7/21/24 17:43:43,877,FPS,76.4,FT Lbs,
7/21/24 17:43:55,870,FPS,75.2,FT Lbs,
7/21/24 17:44:07,870,FPS,75.2,FT Lbs,
7/21/24 17:44:13,893,FPS,79.3,FT Lbs,
7/21/24 17:44:30,865,FPS,74.4,FT Lbs,
7/21/24 17:45:04,868,FPS,74.8,FT Lbs,
7/21/24 17:45:17,877,FPS,76.4,FT Lbs,
7/21/24 17:45:24,879,FPS,76.8,FT Lbs,
7/21/24 17:45:30,875,FPS,76.0,FT Lbs,
7/21/24 17:45:36,879,FPS,76.8,FT Lbs,
7/21/24 17:45:45,870,FPS,75.2,FT Lbs,
7/21/24 17:45:56,881,FPS,77.2,FT Lbs,
7/21/24 17:46:07,884,FPS,77.6,FT Lbs,

Is this a normal deviation for the Ghost outside of that really low 1st shot?

I replaced the Huma gauge with a digital gauge and discovered the reg creeps up to 163b sitting overnight. It settles in to approximately 150-153b between shots. Did I screw something up during the regulator rebuild? Thanks for reading all this if you've made it this far!

 

[Kpac]

I bought a ghost from the classifieds here a while back and noticed it had a slow leak from the weep hole that could actually be heard if in a really quiet room. I utilized this forum and BRK's excellent maintenance videos to troubleshoot and fix the leak by replacing some O-rings on the regulator. I actually completely disassembled, cleaned and replaced all the O-rings since I had it apart anyway. Pretty easy with all the resources available. Put it back together and had no more leaks, yay! But.......after setting the regulator to 150b and shooting a couple hundred pellets through it I've noticed the first shot of the day was slower and had a different POI than follow on shots for the rest of the session. The tiny Huma reg gauge didn't show a pressure change from what I had set but I began to wonder how accurate it was because something is changing. Put the chrony on it and discovered the 1st shot to be way slower than everything after it. Here's the latest 24 shot string:

Shot count: 24
Low: 807
Hi: 893
Avg: 871
STD Dev: 15
Spread: 86

7/21/24 17:40:44,807,FPS,64.8,FT Lbs,
7/21/24 17:41:01,861,FPS,73.6,FT Lbs,
7/21/24 17:41:20,872,FPS,75.6,FT Lbs,
7/21/24 17:41:37,863,FPS,74.0,FT Lbs,
7/21/24 17:41:52,886,FPS,78.0,FT Lbs,
7/21/24 17:42:05,872,FPS,75.6,FT Lbs,
7/21/24 17:42:18,872,FPS,75.6,FT Lbs,
7/21/24 17:42:35,870,FPS,75.2,FT Lbs,
7/21/24 17:43:18,865,FPS,74.4,FT Lbs,
7/21/24 17:43:26,879,FPS,76.8,FT Lbs,
7/21/24 17:43:34,868,FPS,74.8,FT Lbs,
7/21/24 17:43:43,877,FPS,76.4,FT Lbs,
7/21/24 17:43:55,870,FPS,75.2,FT Lbs,
7/21/24 17:44:07,870,FPS,75.2,FT Lbs,
7/21/24 17:44:13,893,FPS,79.3,FT Lbs,
7/21/24 17:44:30,865,FPS,74.4,FT Lbs,
7/21/24 17:45:04,868,FPS,74.8,FT Lbs,
7/21/24 17:45:17,877,FPS,76.4,FT Lbs,
7/21/24 17:45:24,879,FPS,76.8,FT Lbs,
7/21/24 17:45:30,875,FPS,76.0,FT Lbs,
7/21/24 17:45:36,879,FPS,76.8,FT Lbs,
7/21/24 17:45:45,870,FPS,75.2,FT Lbs,
7/21/24 17:45:56,881,FPS,77.2,FT Lbs,
7/21/24 17:46:07,884,FPS,77.6,FT Lbs,

Is this a normal deviation for the Ghost outside of that really low 1st shot?

I replaced the Huma gauge with a digital gauge and discovered the reg creeps up to 163b sitting overnight. It settles in to approximately 150-153b between shots. Did I screw something up during the regulator rebuild? Thanks for reading all this if you've made it this far!

View attachment 482223

Airguns do have sometimes what they call a cold start from sitting for a while and then it happens on the first shot i think the scout rifle is the only rifle you can program around it but think its normal i hope this helps in some way

 

[nervoustrig]

The Ghost uses a balanced valve. I haven't worked on a Ghost so I can't advise specifically but balanced valves are subject to O-ring stiction after sitting up a while. Basically what happens is the valve is slightly harder to knock open on the first shot, as the hammer has to overcome the breakaway friction of a wedged O-ring. The result is similar to that of regulator creep. You can try incrementally increasing the hammer strike to see if it improves enough to not be obtrusive. Otherwise look into supporting the affected O-ring(s) with closer tolerance parts, polishing, and lubrication. The following marathon topic on the FX Impact may be useful to skim over.

Tuning - FX Impact Mk2/M3 - slower first shot - no reg creep - quasi-scientific analysis

Hi guys, Welcome everybody. This is my first post here. I have a problem with my Impact Mk2 PP .30. The reg pressure is 145 bars. When I shoot shot after shot then my v0 is 260m/s. However, when the gun sits for a couple of hours then the first shot is 250m/s despite the exact same reg...

www.airgunnation.com

 

[rc4fun]

Have you rebuilt the regulator? Polished the edges of the washers and the center too? Everything spick and span?
How many shots so far? Cleaned the barrel more than once?

 

[IKnowNutin]

The Ghost uses a balanced valve. I haven't worked on a Ghost so I can't advise specifically but balanced valves are subject to O-ring stiction after sitting up a while. Basically what happens is the valve is slightly harder to knock open on the first shot, as the hammer has to overcome the breakaway friction of a wedged O-ring. The result is similar to that of regulator creep. You can try incrementally increasing the hammer strike to see if it improves enough to not be obtrusive. Otherwise look into supporting the affected O-ring(s) with closer tolerance parts, polishing, and lubrication. The following marathon topic on the FX Impact may be useful to skim over.

Tuning - FX Impact Mk2/M3 - slower first shot - no reg creep - quasi-scientific analysis

Hi guys, Welcome everybody. This is my first post here. I have a problem with my Impact Mk2 PP .30. The reg pressure is 145 bars. When I shoot shot after shot then my v0 is 260m/s. However, when the gun sits for a couple of hours then the first shot is 250m/s despite the exact same reg...

www.airgunnation.com

Thank you for the well articulated reply . Good things to ponder and look at. This rifle didn't have a cold shot issue before I took the reg apart so......I'm wondering if I under lubed some O-rings putting it back together or? I'm familiar with the concept of stiction (breakout force) from my dirt bike days trying to get the front forks as friction free as possible in order to do their job better.

 

[IKnowNutin]

Have you rebuilt the regulator? Polished the edges of the washers and the center too? Everything spick and span?
How many shots so far? Cleaned the barrel more than once?

See 1st post. No polishing performed, just cleaning and O-ring replacement.

 

[Stubbers]

You probably need to resurface the regulators seat (or piston if it has surface imperfection), once a regulator starts creeping, the ideal remedy to return it to a non-creeping (or less creeping) state is to address it.

You didn't experience first shot issues before because your regulator was leaking, which never allowed it to experience creep. The seat is probably beaten up as bad as the o-ring you had to replace...

Balanced valves will 100% experience issues resulting from break away friction as o-rings squeeze the lubricant away from between themselves and the walls and the o-ring itself begins to fill micro-pores within its bore causing adhesion, glass is the only material that will 100% eradicate this that I am aware of.

-Matt

 

[IKnowNutin]

You probably need to resurface the regulators seat (or piston if it has surface imperfection), once a regulator starts creeping, the ideal remedy to return it to a non-creeping (or less creeping) state is to address it.

You didn't experience first shot issues before because your regulator was leaking, which never allowed it to experience creep. The seat is probably beaten up as bad as the o-ring you had to replace...

Balanced valves will 100% experience issues resulting from break away friction as o-rings squeeze the lubricant away from between themselves and the walls and the o-ring itself begins to fill micro-pores within its bore causing adhesion, glass is the only material that will 100% eradicate this that I am aware of.

-Matt

Thanks, that makes sense, too. Looks like I'm taking the reg back out and will be giving it some love.

 

[Stubbers]

Thanks, that makes sense, too. Looks like I'm taking the reg back out and will be giving it some love.

A 10x jewelers loupe or some kind of magnification is great in times such as this where you're dealing with a seat within our pneumatic airguns.

I'd start with wet or oiled 600 grit, one can leave it here and it'll be fine but for regulators, taking it up to 1000 and/or 1500 grit doesn't hurt.

I put my paper on a level surface and run my seat in one direction across the paper a few times, rotate seat 90 degree, repeat. Shouldn't take much to make the seat appear fresh with some sort of magnification.

Not sure how your regulators piston is, if it uses a knifes edge or what and its diameter, so touching up this may not be advised or even necessary, as they're generally a much harder material, but definitely inspect it with magnification prior to ruling out the need to resurface/polish.

-Matt

 

[Corvid_hunter]

Thank you for the well articulated reply . Good things to ponder and look at. This rifle didn't have a cold shot issue before I took the reg apart so......I'm wondering if I under lubed some O-rings putting it back together or? I'm familiar with the concept of stiction (breakout force) from my dirt bike days trying to get the front forks as friction free as possible in order to do their job better.

If it didn't have the issue prior to you working on it, it's likely something that you did or didn't do.

 

[robertwalsh1981]

Thanks, that makes sense, too. Looks like I'm taking the reg back out and will be giving it some love.

Question for you, I am getting ready to take the reg out of my Ghost HP, when you took yours out did you just unthread the regulator adjustment knob (counter clockwise) until it came off to allow access to the regulator for removal?

 

[IKnowNutin]

I don't have the rifle in front of me but if memory serves me correctly, the adjustment knob has an Allen head screw attaching the knob to the adjuster screw and needs to be removed to get access to the regulator. Once the knob is removed the reg should have two holes showing for either a pin wrench or snap ring pliers to unscrew it from the body. BRK has a superb video series detailing the procedure.

 

[robertwalsh1981]

I don't have the rifle in front of me but if memory serves me correctly, the adjustment knob has an Allen head screw attaching the knob to the adjuster screw and needs to be removed to get access to the regulator. Once the knob is removed the reg should have two holes showing for either a pin wrench or snap ring pliers to unscrew it from the body. BRK has a superb video series detailing the procedure.

Cool thank you, I have watched that video a few times unfortunately they already have the knob off and don't make mention of how it comes off. I appreciate the insight to look for an Allen set screw vs my just trying to back it out and then messing up my reg!

Also, not sure why checking the Ghost parts schematic didn't occur to me, found it...