Gunpower stealth 20 shot string
I have bought a gunpower stealth on my FAC certificate and have been delighted with tinkering with it 🙂 I’m running the standard hammer but I do not know the weight and have added 8mm of spring pre-load
Starting pressure 2900 psi shooting bisley magnums AKA kodiaks 21.4 grains and I’m using a 12″ barrel
Keep in mind that I was using a less than adequate light set up
815.6
err
811.1
818.6
831.1
799.0
789.4
797.1
798.7
808.0
err
781.5
784.2
782.3
779.0
776.8
771.6
770.1
770.2
765.4
finish pressure 2100
I think I’m going to remove the spacer to try and level out the string
One question: I plan on getting a 24″ barrel and am wondering what kind of speeds I would get
One question: I plan on getting a
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Viewing 12 replies - 1 through 12 (of 12 total)
I have installed a weaker valve spring because the original was way too stiff which is why I have to use the increased pressures and I don’t fancy taking the valve out again
I have a standard hammer set up no added spring preload or haven’t increased hammer weight. Tophat is at 0.090″ approx (the thickness o a 2 pence piece but I can’t remember my measurment
just shot a group at 30 yards and I am VERY pleased 🙂 I couldn’t even measure the grouping
Dave
I have installed a weaker valve spring because the original was way too stiff which is why I have to use the increased pressures and I don’t fancy taking the valve out again
I have a standard hammer set up no added spring preload or haven’t increased hammer weight. Tophat is at 0.090″ approx (the thickness o a 2 pence piece but I can’t remember my measurment
just shot a group at 30 yards and I am VERY pleased 🙂 I couldn’t even measure the grouping
Dave
On my quest to find the illusive bell curve or the new name of “Up turned bathtub :)) I over filled my gun so i could get partial valve lock and these are my numbers
21.4 grain bisley magnums
Tank filled to 3400 and 8mm spacer removed
576.4
617.5
606.3
591.7
I was getting tired of wasting pellets and dry fired it 6 more times to get a total of 10 shots fired (I swear I have ADD)
Next shot was…….
850.4
I then checked the tank pressure and it was approx 3250 psi
So I then filled to 3300 and fired this string
845.9
857.2
849.5
850.2
850.5
841.7
846.0
836.8
831.1
833.4
823.1
838.8 This shot was taken at a wierd angle to the chrony
824.4
819.3
824.7
812.3
?????? This shot missed the second sensor
814.3
808.5
806.9
I then fired about 5 more shots at some 2×4 :D:D I love seeing splinters fly in all directions theough the scope
End pressure was approx 2500-2600 psi
I think the curve is so steep because Im still only using the 12” barrel and im shooting pretty much max capable velocity
What do you guys think?
I will do some accuracy tests over the weekend hopefully
Dave
EDIT: Just analysed my sting and here are my results
Average speed of 832.3 FPS
Average Energy of 32.9 FPE (With a high of just under 35 FPE
Extreme spread of 50.3 FPS (Quite high for me)
Standard deveation of only 2.1 FPS
Check your numbers for the sd again.
Looks like the valve is maxing from shot one. Must take a hell of a knock to open the valve at those pressures?
Right guys a bit of an update
On my quest to find the illusive bell curve or the new name of “Up turned bathtub :)) I over filled my gun so i could get partial valve lock and these are my numbers
21.4 grain bisley magnums
Tank filled to 3400 and 8mm spacer removed
576.4
617.5
606.3
591.7
I was getting tired of wasting pellets and dry fired it 6 more times to get a total of 10 shots fired (I swear I have ADD)
Next shot was…….
850.4
I then checked the tank pressure and it was approx 3250 psi
So I then filled to 3300 and fired this string
845.9
857.2
849.5
850.2
850.5
841.7
846.0
836.8
831.1
833.4
823.1
838.8 This shot was taken at a wierd angle to the chrony
824.4
819.3
824.7
812.3
?????? This shot missed the second sensor
814.3
808.5
806.9
I then fired about 5 more shots at some 2×4 :D:D I love seeing splinters fly in all directions theough the scope
End pressure was approx 2500-2600 psi
I think the curve is so steep because Im still only using the 12” barrel and im shooting pretty much max capable velocity
What do you guys think?
I will do some accuracy tests over the weekend hopefully
Dave
EDIT: Just analysed my sting and here are my results
Average speed of 832.3 FPS
Average Energy of 32.9 FPE (With a high of just under 35 FPE
Extreme spread of 50.3 FPS (Quite high for me)
Standard deveation of only 2.1 FPS
got a stealth to 18 inch bsa barrel 28 gram hammer about 60 shots 20 m/s extreme spread 30 fpe
Okay I might contact leupy when I have some spare cash to play with hehe 🙂
Ah right. Yeah, for the mags, around 900-950 is best for accuracy. You can order a BSA barrel blank direct from them, though they will probably want to send it to an RFD for you to pick up.
Guy called Lupey can do the barrel work for you, though he ain’t cheap but does a topnotch job.Prob easier just to order the whole shebang from him, save you ordering the barrel. He uses BSA barrels as he claims they are better than LW. Balls. BSA are as good, maybe a little better, but more importantly, they cost half the price of an LW! THATS why he uses them!!
Blodnob no longer makes the valves. A guy in the States does them now. PM selphb to purchase one.
Yeah I do know but that’s where I’m aiming for I would tune it down from supersonic to around 900 fps for the shot count. Any ideas about getting a 24″ .22 barrel in the uk? BSA? I do have a small mini lathe but it’s broken 🙁 at the moment does anyone do them ready cut for a reasonable price? Also howmuch do blodnob valves go for these days?
Man it’s fun blasting pellets through a piece of 2×4 pine 🙂 I’m hoping for about 850-900 fps with the 24″ barrel
Mate, you gonna get alot more than 850-900 fps 😯
Supersonic is around 1100fps.
That’s awesome thanks 🙂 I will try and get another string up without the spacer tomorow to bring the eratic hightower numbers down a bit and get it a bit more consistantly around 800-750 fps
Man it’s fun blasting pellets through a piece of 2×4 pine 🙂 I’m hoping for about 850-900 fps with the 24″ barrel
If you can get 831fps on 12″ 24″ will get them supersonic.
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This is my 5 shot group at 30 yards 🙂 after pumping the gun up and lying in the freezing snow I am very pleased and I don’t think I will touch it until I get a 24″ barrel
http://emob222.photobucket.com/albums/dd320/dave_424/IMG_0129.jpg
Went over my standard deveation and got 9.53 FPS which is okay for me
Im doing some 50 yard and 100 yard shots tomorow so watch this thread