Ghost Ghost HP177 Shot String Data

[tec]

I think this trend clearly shows the (my) Ghost's muzzle velocity increasing as you progress through a shot string, and its due to the plenum pressure steadily falling with each shot..so much so that after two magazines, I changed the PW from 9 to 8 to try and keep the pellets ~900 ft/s.
Is this what others are seeing?
I also took 3 dry fire shots at PW Max to get rid of the overnight Regulator creep (and screwed up and took my first pellet shot on PW Max, so removed that from the shot string data, that one was 983 ft/s)

 

[Solo1]

Have no idea what could cause the problems your seeing except that you have possibly damaged the reg by adjusting so much. My has been setting for several days pulled it out 1st shot 795-805 -810-810-812 and thats how mine goes at pacup they tested velocity both days about middle of match 810 both days?

 

[Solo1]

If i understand your chart thats actually not a bad spread on velocity 10-15 fps isn’t that bad

 

[Franklink]

If i understand your chart thats actually not a bad spread on velocity 10-15 fps isn’t that bad

X2

Lots of talk on the forums of the importance of single digit spread but its importance is vastly over exaggerated.

Keep your spread under about 25fps for regular field target and it'll shoot perfect scores. And I say that based on having shot a handful of perfect scores from an unregulated rifle that has extreme spreads about that large.

 

[tec]

Have no idea what could cause the problems your seeing except that you have possibly damaged the reg by adjusting so much. My has been setting for several days pulled it out 1st shot 795-805 -810-810-812 and thats how mine goes at pacup they tested velocity both days about middle of match 810 both days?

Not disagreeing with you, but unless the o-rings and spring washers weren't properly lubricated, adjusting the regulator should not damage it. Two characteristics [The Basics of Pressure Regulators] of a regulator are creep and *droop. Both can increase with increasing spring compression (for the Huma piston regulator the spring is a stack of Belleville spring disc-washers [Stacking Disc Springs - Belleville Springs]). To damage the regulator you would have to adjust it to the point where you crushed-compressed washers to the point where they lose "stiffness". Hence, why I have ask both BRK and Daystate in multiple forums and via email (multiple times with no responses) what if any is the upper limit of regulator-plenum set pressure. Going to try Huma next.
Those shots were done with set point of ~140 bar, I am going to change the set point to ~130 bar and see if the creep and drop reduce. I am also going to crunch the numbers and will post that too.
*I would have expected with decreasing bottle/source pressure the outlet pressure of the regulator would increase, not decrease, even if it was a balanced poppet regulator [Managing Supply Pressure Effect in Regulators]. I will ask Huma about this too...

 

[tec]

If i understand your chart thats actually not a bad spread on velocity 10-15 fps isn’t that bad

Agree, except I change the PW from 9 to 8 half way in....in hindsight I should have left it at 9 to better show the change in P and V over the 4 consecutive magazines.

 

[tec]

X2

Lots of talk on the forums of the importance of single digit spread but its importance is vastly over exaggerated.

Keep your spread under about 25fps for regular field target and it'll shoot perfect scores. And I say that based on having shot a handful of perfect scores from an unregulated rifle that has extreme spreads about that large.

Cole, as you know I am noob here having only shot my air rifles in my back yard...How many shots are in a FT round? How many rounds make a match? Can you make a PW adj during a round? Can you take shots between rounds to make adjustments? What distance should I zero my scope? Is there an article on FT that you recommend that would answer all my questions and prevent me from annoying everyone here on HAM?
Cheers
tc

 

[tec]

Not disagreeing with you, but unless the o-rings and spring washers weren't properly lubricated, adjusting the regulator should not damage it. Two characteristics [The Basics of Pressure Regulators] of a regulator are creep and *droop. Both can increase with increasing spring compression (for the Huma piston regulator the spring is a stack of Belleville spring disc-washers [Stacking Disc Springs - Belleville Springs]). To damage the regulator you would have to adjust it to the point where you crushed-compressed washers to the point where they lose "stiffness". Hence, why I have ask both BRK and Daystate in multiple forums and via email (multiple times with no responses) what if any is the upper limit of regulator-plenum set pressure. Going to try Huma next.
Those shots were done with set point of ~140 bar, I am going to change the set point to ~130 bar and see if the creep and drop reduce. I am also going to crunch the numbers and will post that too.
*I would have expected with decreasing bottle/source pressure the outlet pressure of the regulator would increase, not decrease, even if it was a balanced poppet regulator [Managing Supply Pressure Effect in Regulators]. I will ask Huma about this too...

From Huma page:

Not sure why BRK hasn't published something like this, they have to have it, as they had to determine hammer weight, hammer spring stiffness (for 5 now 6 diff springs)....

 

[Solo1]

@ Tec. You say you’re new to airguns but you seem to be analysing this as an engineer. Quite frankly you are in my opinion over analysing. Set the gun to some pressure and shoot it for a while to break everything in have you shot a thousand pellets yet? New guns settle in after shooting a while i know mine did perhaps you’re not giving it that chance.

As far as ft most matches are 40 or 60 shot matches and if you look on here or airgun nation you can find plenty to read to get you started understanding ft! Best thing is to try to go and shoot 1 this spring as its a lot of fun!

 

[tec]

@Solo1....damn its that obvious? haha yes ChE been working in the industrial gas business for ..too long, well acquainted with pneumatics, regulators etc...so trying to determine the performance characteristics of the pressure regulator-hammer valve-valve system of my rifle...
1000, no not yet, maybe 600 ish
The plan is to one day go to a FT shoot...when I have my Ghost properly tuned, and scope ranged...
Greatly appreciate the feedback/comments that you and others take the time to give
tc

 

[Solo1]

Just set your 177 to 135 bar pw 6 and shoot some jsb mrd 13 gr’s should be close to 810 fps ( adj to below 815 ) and pratcice shooting off styx with a seat of your choice. Field target is a whole lotta fun as far as im concerned! Oh and thats for the hp barrel with .047 or med spring

 

[tec]

Just set your 177 to 135 bar pw 6 and shoot some jsb mrd 13 gr’s should be close to 810 fps ( adj to below 815 ) and pratcice shooting off styx with a seat of your choice. Field target is a whole lotta fun as far as im concerned! Oh and thats for the hp barrel with .047 or med spring

125 bar, PW 11, def tighter groups than BM
177 JSB Ex M 13.43 , JSB Ex Monster Redesign

Shot count: 10

Low: 802 FPS
Hi: 814 FPS
Avg: 809 FPS
Spread: 12 FPS
STD Dev: 4.1 FPS

16-Dec-2023 13:40:58,814,FPS,19.8,FT Lbs,
16-Dec-2023 13:41:36,805,FPS,19.3,FT Lbs,
16-Dec-2023 13:42:05,807,FPS,19.4,FT Lbs,
16-Dec-2023 13:42:46,812,FPS,19.7,FT Lbs,
16-Dec-2023 13:43:13,802,FPS,19.2,FT Lbs,
16-Dec-2023 13:44:40,811,FPS,19.6,FT Lbs,
16-Dec-2023 13:45:21,809,FPS,19.5,FT Lbs,
16-Dec-2023 13:45:43,803,FPS,19.2,FT Lbs,
16-Dec-2023 13:46:27,812,FPS,19.7,FT Lbs,
16-Dec-2023 13:47:01,813,FPS,19.7,FT Lbs,

 

[tec]

125 bar, PW 11, def tighter groups than BM
177 JSB Ex M 13.43 , JSB Ex Monster Redesign

Shot count: 10

Low: 802 FPS
Hi: 814 FPS
Avg: 809 FPS
Spread: 12 FPS
STD Dev: 4.1 FPS

16-Dec-2023 13:40:58,814,FPS,19.8,FT Lbs,
16-Dec-2023 13:41:36,805,FPS,19.3,FT Lbs,
16-Dec-2023 13:42:05,807,FPS,19.4,FT Lbs,
16-Dec-2023 13:42:46,812,FPS,19.7,FT Lbs,
16-Dec-2023 13:43:13,802,FPS,19.2,FT Lbs,
16-Dec-2023 13:44:40,811,FPS,19.6,FT Lbs,
16-Dec-2023 13:45:21,809,FPS,19.5,FT Lbs,
16-Dec-2023 13:45:43,803,FPS,19.2,FT Lbs,
16-Dec-2023 13:46:27,812,FPS,19.7,FT Lbs,
16-Dec-2023 13:47:01,813,FPS,19.7,FT Lbs,

Should have said LP spring