Ultralight SSH 2400KT tests

[Tack Driver 10]

Started making Sling Shot Hammers from peek about a month ago.
https://www.gatewaytoairguns.org/GTA/index.php?topic=102095.msg156573861#msg156573861
Now it's time to run some tests in a gun to see the result.

The test subject is a 2400KT that I converted to PCP.
Got it from Rob, aka Spooner, in a trade for some custom pumper parts.

It's a basic gun with only a 32cc reservoir, half the volume of a Prod.
14 1/2" Crosman/LW 177 cal choked barrel, .125" TP.
Swapped the 13xx trigger for a 1701 trigger.
Made the valve from 7075 aluminum, .187" throat, flat seat, .140" port.
The valve stem is made from PAI, .220" diameter on a 1/8" shaft.
15.45g peek hammer, peek SSH with a disco spring.
Ran it earlier this month and made 24 shots at 13.72 FPE average.
More testing to follow.

[anti-squirrel]

Looks nice a nice set of results ya got there.

Someday way down the road I may PCP-ify my 2400KT.  Results like yours add fuel to that fire.

[Tack Driver 10]

Looks nice a nice set of results ya got there.

Someday way down the road I may PCP-ify my 2400KT.  Results like yours add fuel to that fire.

The 2400 makes a great platform for a PCP pistol.
Works good as a pistol or a carbine.
Only negative might be the small reservoir.
With efficiency improvements this gun can get good power/shot count.

With that in mind swapped the TP from .125" to .120".
This decreased the power and increased the shot count.

Gun makes 12 FPE with 30 shots in .177 cal.
Installed a 14 1/2" .22 cal LW barrel, same TP etc.
Makes 28 shots at 13.80 FPE.

[Tack Driver 10]

The gun is performing really good with this valve.
Want to try a few things before I settle on this configuration.
Made a new brass valve, pulled the current valve and installed the new one.

This valve has a .125" throat with a peek stem, 1/16" shaft, .090" TP.
It fires very easy due to its small throat diameter.
There's only 37lbs of pressure holding it closed at 3K psi.
The first valve with a .187" throat had 83lbs on it.

The mini-me hammer is 5.30 grams vs 15.45 grams for the full size hammer used on the original valve.
Could only manage 24 shots before the spread opened up.
I believe the low pressure on the valve just isn't enough to hold it closed over a wide shot count.
I can't lighten the hammer any more so need to increase the throat diameter.
Total SSH flying weight is under 10 grams including 1/3 spring weight.

[Hack21]

Looks like a fun build Ron!  The calculated efficiency at 1.9 was very consistent between the three configs.  The parts look great as usual.  And talk about hand pump friendly. 

[threesuns]

Wish I had the knowledge and skills for that kind of tinkering. My .25 DAQ (22xx platform) has been on hold for a while pending a power plant. Middle

[Tack Driver 10]

Looks like a fun build Ron!  The calculated efficiency at 1.9 was very consistent between the three configs.  The parts look great as usual.  And talk about hand pump friendly.

Hi Eric,

This gun has been a lot of fun to toy with.
The last run with the 1/8" valve throat blew me away.
The first time I took a shot I used the Ghost Gun SSH adjusted straight from the bigger 3/16" throat.
It made 930 FPS, 16 FPE and was pretty loud, had to detune it to get a decent shot string.

I decided to open the throat to .156", about half way between 1/8" and 3/16".
That should put me in the sweet spot.
Been real cold here, 1 degree this morning but should be able to test it this weekend.

[Tack Driver 10]

Wish I had the knowledge and skills for that kind of tinkering. My .25 DAQ (22xx platform) has been on hold for a while pending a power plant. Middle

Hi Timothy,

I have two DAQ breeches, they're fantastic.
What's missing from the DAQ gun?
Looks like a Prod tube so a valve should be easy to find.

The top gun looks like a 2400KT PCP?
If so what kind of performance are you making with it?

[threesuns]

What's missing from the DAQ gun?
Looks like a Prod tube so a valve should be easy to

DAQ .25 is actually a Disco tube cut to match upper. I have a Cothran Power House valve and think that would best pair with a lite weight SSH to get any kind of shot count.

The top gun looks like a 2400KT PCP?
If so what kind of performance are you making with it?

I call that my 2401. 1701 barrel, shortened Baker breech, Prod hammer, adjuster and trigger group. 2400 PCP tube mod. My solder filled valve and TP. I’m getting just shy of 40 shots at 500fps / 4.5fpe

[Mzq284]

This is a great thread, you guys are creating my next project for me! Thanks!

[Tack Driver 10]

Been working on this gun trying different valve seal diameters.
Basically hit or miss like trying to find your way out of a maze in the dark.
Decided it's time to get this down to more of a science.
I'm not a math wizard by any stretch but here goes.

Ran a string to determine the optimal pressure range with an acceptable ES.
With a .187" diameter valve seal this guns operating range is 2800-1400 psi.
Take the area of .187" (.0275) and multiply it by 2800 and 1400 to define the pressure range on the valve stem.
 2800=77
 1400=38
So the gun in its current configuration operates optimally with between 77-38 lbs. of pressure on the valve stem.

I want my valve to operate in the high end of the guns pressure limit of 3K psi.
Take 77 psi and divide it by 3K to get the area of the new valve seat, .0256.
Multiply the area .0256 x 3.14, the square root of this is the radius, multiply it by 2 to get the diameter of .180" the new valve seal.
77 divided by .0256=3008 psi
38 divided by .0256=1484 psi
Subtract 1484 from 3008=1524 psi, this is the useable pressure.
1524 psi divided by 50 psi=30.
So a gun that uses 50 psi per shot should get around 30 shots.

Opened the brass valve seal to .180", using a 1/8" shaft with a PAI stem.
Made 29 shots @ 12.29 FPE average.

Without spending a disproportionate amount of time on this I think this is very good.
When I first started this project thought 20 x 12 FPE would be a reasonable goal.
May tinker with it a little more but for now stick a fork in it.

[Tack Driver 10]

In an effort to increase shot count made a new valve with a .172" throat.
It should fire at higher pressure and increase the shot window.

Decreased HT (.580->.550) and hammer weight (15.45->13.60) and made 38 shots at 11.82 FPE average.
Total 450 FPE with an ES of 43, at 30 yds vertical POI shift is .120", at 40 yds .260".
Gun is very back yard friendly, 76 dB at 3' with a trail baffle based moderator.

The burning question.....does this render CO2 obsolete?

[aluminumfetish]

Can I ask... how it the valve stem bonded to the poppet ? Is it a tight fit or loc-tite or something ?

Thanks.

[Tack Driver 10]

The poppet is drilled .122" and a .125" drill blank is pressed in ~3/16".
No glue or any other prep, so yes, tight fit.

[Mzq284]

Pretty incredible results. I've wanted a hpa pistol for a while, this is a good future project, I'm watching with extreme interest.
No, it doesn't totally obsolete CO2, but it sure does take a bite out of CO2 use.

[Tack Driver 10]

Pretty incredible results. I've wanted a hpa pistol for a while, this is a good future project, I'm watching with extreme interest.
No, it doesn't totally obsolete CO2, but it sure does take a bite out of CO2 use.

The 32cc reservoir produced a 38 shot string spanning 2K psi with only a 43 ES.
It's like the gun is self regulating, like the Energizer Bunny, it keeps going and going and going.

I may try converting a 2300 to PCP.
It has a ~24cc reservoir so should be able to get about 25 decent power shots around 11 FPE.
Detuned should get 50+ low power shots around 5 FPE.

I can transfer the valve and SSH etc. from the 2400 so would be very easy. 
Just need to drill the 2300 tube to pin the valve.

[Mzq284]

That 2300 would make a slick target pistol, or a cool plinker. I looked at your first graph in 22 again, that was pretty good right there. It would make a good small game hunter. It performs almost identical to my 3622, and it's no slouch. I'm on the hunt for a 2400 tube.

[Tack Driver 10]

Although the gun is very efficient at ~12 FPE it can be cranked up.
During testing with the .172" throat and 1/16" shaft stem it made 1045 FPS, 20.56 FPE.
That was with 8.4 JSB and the 11g hammer.

With 8,.4 JSB and 8g hammer with peek striker, 945 FPS, 16.65 FPE.

With 13.4g pellets and 8.3g hammer:
903 FPS, 24.26 FPE.

Way too much power for this small lightweight gun but it's there if you want it.

Here's a sneak peek at my next project.

[Back_Roads]

 
 Ron you never cease to amaze me the way you know you way around tuning these guns 

[Mzq284]

I just bought my son a 2240 for a build, it's a Chinese gun. The tube is etched, not the heavy roll stamp. I'm wondering how it would work for a small hpa plinker. Once it's torn down, I'm going to commandeer the tube and try it.
That's going to be a neat pistol, I'm itching to see what you come up with, your builds don't disappoint.