Ghost YOUR GHOST TUNE share and care thread

[Solo1]

I’ve done a bit of shooting with the 177 ghost hp and these are some numbers I’ve gotten in testing i also believe that daystate designs their valve to work optimally from around 130-150 bar.
Some numbers for anyone interested in the 177 hp Ghost
With the light spring
13 gr h&h slugs 770-930 140 bar
16 gr h&n slugs 625-830. “
16 gr jsb pellets 930. 140 bar
With stock spring
13 gr h&n slugs 940-975 160 bar
16gr h&n slugs 840-900. 160bar
20 gr h& n slugs 840 on max 160 bar
With the light spring and 140 bar i get 805 wheel on 3 with 13gr jsb

Ive also shot the gun all year till the pa cup at 80 bar with 13 gr jsb and it shot extremely well though the hammer wheel did nothing i now have the gun set to 135 bar and on pw 6 i get 805 fps with the 13 jsb and push 13 h&n slugs to 900 i believe pw max

 

[Franklink]

I’ve done a bit of shooting with the 177 ghost hp and these are some numbers I’ve gotten in testing i also believe that daystate designs their valve to work optimally from around 130-150 bar.
Some numbers for anyone interested in the 177 hp Ghost
With the light spring
13 gr h&h slugs 770-930 140 bar
16 gr h&n slugs 625-830. “
16 gr jsb pellets 930. 140 bar
With stock spring
13 gr h&n slugs 940-975 160 bar
16gr h&n slugs 840-900. 160bar
20 gr h& n slugs 840 on max 160 bar
With the light spring and 140 bar i get 805 wheel on 3 with 13gr jsb

Ive also shot the gun all year till the pa cup at 80 bar with 13 gr jsb and it shot extremely well though the hammer wheel did nothing i now have the gun set to 135 bar and on pw 6 i get 805 fps with the 13 jsb and push 13 h&n slugs to 900 i believe pw max

I agree about the valves optimally functioning mostly in that window you mention. Been too long for me to remember exactly but seems like I needed slightly lower for the .177 Carbine barrel and 19fpe.

So for my uses in .177, .20, and .22 (basically 18-50fpe) I've found reg pressures in the 120-145 bar range to be optimal.

 

[Solo1]

I agree about the valves optimally functioning mostly in that window you mention. Been too long for me to remember exactly but seems like I needed slightly lower for the .177 Carbine barrel and 19fpe.

So for my uses in .177, .20, and .22 (basically 18-50fpe) I've found reg pressures in the 120-145 bar range to be optimal.

120 is quite possible with the short barrel light spring and 10 gr jsb and pw 1 with the longer barrel and 13 gr jsb i could probably go there too just on a different pw setting

 

[tec]

Choked flow occurs when downstream pressure is (0.528) x (Upstream pressure).....so optimal Regulator Set Pressure for fastest recharge rate would be (0.528) x (Min Bottle Pressure before Refill). So for me, at 200 Bar Refill pressure, 105.6 bar would be optimal Reg pressure for fastest fill rate, or at least that is what the math would say.... By setting my Regulator for 200 Bar, I am definitely slowing down the recharge rate.
The nature of the Ghost's design is that the higher the Regulator Pressure the larger the spread between Min and Max on the Power Wheel. While on the above chart it only looks like I have 50 ft/s between Min and Max, but that isn't accounting for the pellet weights. Shooting a Heavy at PW Max with a 200 Bar set press is >1200 ft/s, >300 ft/s spread. Lowering the Reg pressure would increase the Lighter Pellets velocity to above 900 ft/sec, I was looking for a "tune" that would allow any of those pellets to be shot and not have to do a hammer spring change out.
I plan on experimenting to find the "tune" that will give me the most repeatable performance for the JSB Heavy sub 20 ft-lb.
I just shot (7) 13 shot magazines of the diff pellets, and the bottle went from 250 - 200 bar. So that was with a range of PW settings from 3 to Max for an idea of air consumption. Distance was 36 yards, and except for the Beast's, not exactly happy with the precision. My .22 Revere with JSB Exact Jumbo is one ragged hole 5 shot group at 36 yards. SI is "sight in", the others correspond to the pellet and order in which they were shot. B7, 8, 9 are the Beasts, B7 it put 2 in one hole, then 3 in a different hole...and then settled into a much tighter groups. MDR5, I moved the aim point to the "8" because the 3rd shot aiming at the bull when through the backstop and hit the shed (cardboard box of Vigoro rubber mulch, it settled and bulged the box and I was too lazy to redistribute it when I was setting up...that will learn me, now I have to patch an almost hole in the shed).

 

[Solo1]

Well i have no idea what you’re talking about in the beginning there but if your revere is regulated check what its set at and i bet it says 140 bar i know thats what mine is set at

 

[Franklink]

I understand now.

You're doing the same thing (just taking it to the extreme) I am with the .20/13.73, taking advantage of the fact that a relatively high reg pressure actually restricts power with lighter pellets and reduced hammer spring tension.

As in my setup, it's less than ideal to run higher than necessary reg pressure for the low power tune, but it opens up the possibilities of dialing up the power quite a bit with heavier projectiles and more hammer spring tension.

Your power range seems to be about 18-31fpe in .177.
Mine with the .20 is 19-32fpe, so similar. But I'm getting there with a 128bar reg pressure.

Remind me, is your .177 barrel the carbine/plus length, or the HP?

Another thought is how much harder it is to make power in .177 than bigger calibers, less surface area (cross section) for the air to act on.

And an additional thought is transfer port size. I haven't measured, but from past discussions with my machinist buddy, he likes 70% of bore size for the tp in the barrel. So I'd assume the tp in my .20 is 70% of .20. The .177 carbine barrel has a pretty tiny transfer port, another factor working against making power.

If your barrel is an HP, I'd love to know the diameter of the transfer port, and if it's oval or round.

 

[Solo1]

I understand now.

You're doing the same thing (just taking it to the extreme) I am with the .20/13.73, taking advantage of the fact that a relatively high reg pressure actually restricts power with lighter pellets and reduced hammer spring tension.

As in my setup, it's less than ideal to run higher than necessary reg pressure for the low power tune, but it opens up the possibilities of dialing up the power quite a bit with heavier projectiles and more hammer spring tension.

Your power range seems to be about 18-31fpe in .177.
Mine with the .20 is 19-32fpe, so similar. But I'm getting there with a 128bar reg pressure.

Remind me, is your .177 barrel the carbine/plus length, or the HP?

Another thought is how much harder it is to make power in .177 than bigger calibers, less surface area (cross section) for the air to act on.

And an additional thought is transfer port size. I haven't measured, but from past discussions with my machinist buddy, he likes 70% of bore size for the tp in the barrel. So I'd assume the tp in my .20 is 70% of .20. The .177 carbine barrel has a pretty tiny transfer port, another factor working against making power.

If your barrel is an HP, I'd love to know the diameter of the transfer port, and if it's oval or round.

.0055 diameter as best as i can tell is the port in the barrel.

 

[Franklink]

.0055 diameter as best as i can tell is the port in the barrel.

Gotta be 0.055, not 0.0055.

Even 0.055 is only 31% of bore size. (0.177x 0.31 = 0.05487).

Round? Not oval?

 

[Solo1]

Gotta be 0.055, not 0.0055.

Even 0.055 is only 31% of bore size. (0.177x 0.31 = 0.05487).

Round? Not oval?

round

 

[Solo1]

Sorry cole my caliper wasn’t calibrated right .129 “ is best i can get a 1/8 drill bit fits in backward with the slightest bit of movement just under 73%

 

[Franklink]

Sorry cole my caliper wasn’t calibrated right .129 “ is best i can get a 1/8 drill bit fits in backward with the slightest bit of movement just under 73%

That sounds much better. 0.177x0.73 = 0.12921 so you're talking about 73% of bore size here.

Interesting. Thanks for measuring.

 

[tec]

Well i have no idea what you’re talking about in the beginning there but if your revere is regulated check what its set at and i bet it says 140 bar i know thats what mine is set at

Fluid flow. When trying to flow a gas through a valve (restriction) when the upstream press is ~2x the downstream, the flow goes sonic in velocity and “chokes”, decreasing the down stream press will not change the flow rate.
So by having a reg press of 200 bar, I was trying (poorly) to explain why my recharge rate was slow vs a lower reg pressure, and at same time explain the upper limit for fastest recharging.
Yes, Revere is regulated, but she beats the hell out of my Gammo resettable field target targets, and my metal pellet trap, hence obtaining the Ghost. Now that I have the .22 barrel kit …I will probably sell her, as I don’t expect to be shooting her very much.

 

[tec]

I understand now.

You're doing the same thing (just taking it to the extreme) I am with the .20/13.73, taking advantage of the fact that a relatively high reg pressure actually restricts power with lighter pellets and reduced hammer spring tension.

As in my setup, it's less than ideal to run higher than necessary reg pressure for the low power tune, but it opens up the possibilities of dialing up the power quite a bit with heavier projectiles and more hammer spring tension.

Your power range seems to be about 18-31fpe in .177.
Mine with the .20 is 19-32fpe, so similar. But I'm getting there with a 128bar reg pressure.

Remind me, is your .177 barrel the carbine/plus length, or the HP?

Another thought is how much harder it is to make power in .177 than bigger calibers, less surface area (cross section) for the air to act on.

And an additional thought is transfer port size. I haven't measured, but from past discussions with my machinist buddy, he likes 70% of bore size for the tp in the barrel. So I'd assume the tp in my .20 is 70% of .20. The .177 carbine barrel has a pretty tiny transfer port, another factor working against making power.

If your barrel is an HP, I'd love to know the diameter of the transfer port, and if it's oval or round

Gotta be 0.055, not 0.0055.

Even 0.055 is only 31% of bore size. (0.177x 0.31 = 0.05487).

Round? Not oval?

177 HP. Mine is oval. 3.36 x 3.17 mm A=3.36/2x3.17/2xpi =8.36mm2. Stem opening is 3.13mm = 7.69mm2

177 HP flow through probe with oval transfer port. measurement in mm
"A"= 3.36; "B"=3.17 mm
Area = (3.36/2) x (3.17/2) x pi =8.36mm2.
Stem opening is 3.13mm
Area = pi*r^2=7.69mm2



"A" axis measurement of oval

"B" axis measurement of oval


End of probe opening measurement

 

[tec]

177 = 4.495 mm so 15.87mm2 8.36/15.87=52.6%
Stem 7.69/15.87= 48.5%

 

[Franklink]

@tec, the flow-through type probe is certainly a choke point so very relevant.

What do the measurements on the transfer port through the barrel look like?

 

[Danman]

Fluid flow. When trying to flow a gas through a valve (restriction) when the upstream press is ~2x the downstream, the flow goes sonic in velocity and “chokes”, decreasing the down stream press will not change the flow rate.
So by having a reg press of 200 bar, I was trying (poorly) to explain why my recharge rate was slow vs a lower reg pressure, and at same time explain the upper limit for fastest recharging.
Yes, Revere is regulated, but she beats the hell out of my Gammo resettable field target targets, and my metal pellet trap, hence obtaining the Ghost. Now that I have the .22 barrel kit …I will probably sell her, as I don’t expect to be shooting her very much.

OK now you have me confused too ....you will possibly sell the .22 revere (30fpe?) bc it's beating up your targets but will keep the ghost which you have set up for .177 but you also have a .22 barrel now for it, and that gun can (and easily does) crush 20 fpe in .22?! From a financial (and simplified) view point I suppose the .22 barrel vs keeping the revere makes sense. Long term I do wonder what the high pressures may do to the guns seals....let us know?

 

[Franklink]

@tec, by sharing the dimensions on the .177 flow through probe you've created an interesting question.....do the .177 HP Ghosts have a pin type probe, or a flow through probe?

In theory, a pin probe should be capable of more power, considering the chokepoint nature of the reduction in airway passageway through the flow through probe, as presented by @tec a few posts ago.

Although some of the air from the shot is likely making it around the outside of the flow through and getting to the back of the pellet.

Extended pin probe on left, flow through probe on right.

 

[Solo1]

Just for giggles i just shot a couple 16 gr jsb on max hw and got an average of 885. This is my ft tune with 13gr jsb 135 bar pw 6 810 fps. 885 equals 28 fpe and about 19.5 with the 13’s all on the light spring.

 

[tec]

OK now you have me confused too ....you will possibly sell the .22 revere (30fpe?) bc it's beating up your targets but will keep the ghost which you have set up for .177 but you also have a .22 barrel now for it, and that gun can (and easily does) crush 20 fpe in .22?! From a financial (and simplified) view point I suppose the .22 barrel vs keeping the revere makes sense. Long term I do wonder what the high pressures may do to the guns seals....let us know?

Yes correct,the .22 Revere is 30+ ft-lb, the Ghost..I can easily adjust that to be sub 20. I have no need for more ft-lb right now.
Seals: I have inquired at BRK (multiple times multiple ways )and AoA on the design limits and expected operating parameters given the 5 different hammer springs, barrel lengths and regulator adjustability and BRK has "ghosted" me..haha...AoA says that don't know. As long as the Orings are properly lubricated they should be fine. The valve and the hammer are doing all the "work".

 

[tec]

@tec, by sharing the dimensions on the .177 flow through probe you've created an interesting question.....do the .177 HP Ghosts have a pin type probe, or a flow through probe?

In theory, a pin probe should be capable of more power, considering the chokepoint nature of the reduction in airway passageway through the flow through probe, as presented by @tec a few posts ago.

Although some of the air from the shot is likely making it around the outside of the flow through and getting to the back of the pellet.

Extended pin probe on left, flow through probe on right.
View attachment 3297

177 flow through like probe you are holding, .22 pin like the probe to the left. The "oval" hole on the probe looks modded, yes? The photos I posted, I measured the 2 axises of the oval transfer port on the probe and outlet round port at the end of the probe. I updated that post to be more clear