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PostPosted: Tue Mar 04, 2014 7:25 am 
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Location: 123 gun street Nova Scotia
you should be getting+/- 480f/s with the .357 if your valve/hammer is set up for it , seems like you will have lots of volume now.


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PostPosted: Tue Mar 04, 2014 9:03 am 
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jezX wrote:
you should be getting+/- 480f/s with the .357 if your valve/hammer is set up for it , seems like you will have lots of volume now.


I can't imagine how loud that's going to be out of a 12" barrel !


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PostPosted: Tue Mar 04, 2014 12:13 pm 
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jezX.... I pretty surprised you can get than kind of power from a 12.5" barrel on CO2 at room temperature, but I assume you are speaking from experience.... How big were your ports?.... Was that roundball or bullets/pellets, and what weight?.... With RB, that is 35 FPE.... I hope to try the 28" rifle barrel in .35 cal later today....

Bob

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Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since!
Airsonal;
Too many! Springers, Pumpers, CO2, but I love my PCPs and developing them!
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PostPosted: Tue Mar 04, 2014 9:21 pm 
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I bored out the 2240 valve back end to 0.62" ID, so my total valve volume is now about 11 cc including the area around the neck of the cartridge.... I assembled the bottom end and tested for leaks.... It was good to go, so I bolted on the breech from my Disco Double with the .357 barrel (28") and proceeded to test the velocity at various preloads.... It got close to 500 fps at coil bind, but there was no plateau, so I needed more hammer strike to find the maximum possible with this combination of valve volume and porting.... All I had to do was drop in a stock Disco hammer to go along with the Disco spring I was already using, and that provided enough to show a plateau in the power curve, at 515 fps using the 78 gr. JSB pellets (46 FPE).... Here is the way the gun reacts to changing the preload, followed by a shot string at 5 turns out from coil bind on the preload....

Image

As you can see, you don't get very many shots from a cartridge at these power levels.... The 6 good shots averaged 485 fpe (42 FPE), and I tested the gun with a 67 gr. roundball and it shot 555 fps, so the gun would have to be detuned to be a non-PAL rifle.... To be at all practical, it would need to have a longer tube with two cartridges, or be bulk fill, which I can do with the same valve, by just installing a Disco fill fitting.... At least now there is the possibility of making a workable CO2 pistol in .35 cal shooting roundball somewhere in the (mid?) 400s so I wil try that at a later date....

In the meantime I'm convinced I now have enough power to make the .30 cal pistol a viable project, so the next stage is to fit my 12.5" barrel and make a new bolt (or at least bolt nose) so that I can find out how that will perform.... It would appear that my earlier concerns about not enough power for a pistol larger than .25 cal shooting close to the 500 fps non-PAL limit may have disappeared by having more CO2 volume available for the shot....

Bob

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Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since!
Airsonal;
Too many! Springers, Pumpers, CO2, but I love my PCPs and developing them!
Proud Member of the 2000+fps Club!


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PostPosted: Tue Mar 04, 2014 10:46 pm 
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Real nice Bob. Im sure with your preload playing youll tune it around the 495ish area..

When I did mine years back for rnd ball. Mine was bulk filled with something around 0.200 port size IIRC. Tube and valve was from a Cr 262 about 2" longer than a 2250 tube. IIRC shot count wasnt over 20 ish. But never tuned it for a plateau. Didnt have a chrony back then....Sold it south of the border. Shortly after. :cry: Made for quite the camping can killer that summer...lol.. :twisted:

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PostPosted: Tue Mar 04, 2014 11:42 pm 
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Once I decide on a caliber and tune, I'll remove the RVA and install a fixed end cap with spring and guide so that there is no external adjustment, and yes, it will defintely be tuned under 500 fps....

Bob

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Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since!
Airsonal;
Too many! Springers, Pumpers, CO2, but I love my PCPs and developing them!
Proud Member of the 2000+fps Club!


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PostPosted: Thu Mar 06, 2014 11:54 pm 
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I machined the .300 cal 12.5" barrel today and got it mounted in the breech.... I determined the velocity with various preload settings and graphed it, decided I would tune the gun to 7 turns out on the preload and shot a string.... I checked the velocity using roundball and it was JUST under 500 fps, and at 39.6 gr. those are lighter than any available pellet, so I replaced the RVA with a fixed cap with a custom fitted spring guide to set the velocity the way it was at 7 turns out.... Here are the results....

Image

I'm getting 10 good shots between 458 and 470 fps, and the average is 466 fps (21.6 FPE).... The velocity falls off when I warm the gun over about 75*F and seems to peak at about 60*F, falling again slowly after that, so the valve is self-regulating very well, which results in the very flat shot string.... The gun is relatively insensitive to rate of fire for three quick shots before the velocity drops on the 4th about 10 fps.... This is one of the advantages of tuning a CO2 gun in this manner....

I plan to make a longer tube from a 2260 tube to hold two CO2 cartridges, and that should give me three full 7-shot magazines before the power drops off, and the tube will still be a couple of inches shorter than the barrel.... I'm VERY pleased with the development of this pistol, and now that I have about 11 cc available for the valve to draw from I have a working non-PAL pistol in .300 cal, and it can also be made into a non-PAL rifle in .357 cal.... with twice the power but half the shots.... I think I have reached the limits of this build, and I have no plans to bother setting the gun up with the .357 cal 12.5" barrel I have.... I'm so pleased with the way it shoot in .30 cal, and the projected shot count with two cartridges, I just don't see any point....

Bob

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Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since!
Airsonal;
Too many! Springers, Pumpers, CO2, but I love my PCPs and developing them!
Proud Member of the 2000+fps Club!


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PostPosted: Fri Mar 07, 2014 6:30 am 
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Fantastic result Bob. Congratulations!


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PostPosted: Fri Mar 07, 2014 6:50 am 
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i thought you said you had the longer barrel on ... maybe i read to quickly :) for a 12'' barrel that would be alot .
the 28'' barrel is what i was think of . 3000psi id bet you'd get over 500f/s with 12'' barrel . i have a couple .357 short barrels i may have to try at 12''
the 515 f/s seems reasonable for the 28'' barrel , higher then id expect , but i assume you'l be finding out soon :)


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PostPosted: Fri Mar 07, 2014 10:38 am 
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Location: Okanagan,BC
Another amazing build!

Any pics of the almost completed project?

8)


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PostPosted: Fri Mar 07, 2014 11:43 am 
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jezX.... Yeah, I can get over 500 with the 28" barrel on CO2, in fact 555 with roundball, so mid 400's might be possible with the 12.5" barrel in .357.... With HPA pretty much anything is possible, how much pressure do you want to run?.... *LOL*.... but this was meant to be a CO2 project to get reasonable shot count, and that's pretty tough when you combine pistol, big caliber, and big power on HPA without tethering....

wllm995.... The gun still looks exactly the same as the photo at the bottom of page 1, I still haven't blued the barrel.... It now has a non-adjustable end cap, set for non-PAL velocities with the .300 cal barrel....

Bob

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Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since!
Airsonal;
Too many! Springers, Pumpers, CO2, but I love my PCPs and developing them!
Proud Member of the 2000+fps Club!


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PostPosted: Fri Mar 07, 2014 3:12 pm 
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Make those cans dance !!!

Image

Exit hole on soup can, with entrance hole visible on the other side.... This thing sure packs a whallop !!!

Bob

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Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since!
Airsonal;
Too many! Springers, Pumpers, CO2, but I love my PCPs and developing them!
Proud Member of the 2000+fps Club!


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PostPosted: Fri Mar 07, 2014 7:11 pm 
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Location: Victoria, BC and Clarkston, WA
rsterne wrote:
Make those cans dance !!!

Image

Exit hole on soup can, with entrance hole visible on the other side.... This thing sure packs a whallop !!!

Bob


Bet the darn gun ahs a little bit of recoil!
Do you lose the target in the scope from muzzle jump?

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Pardini K10
Brocock Concept .22
3 Custom Crosman 2260
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PostPosted: Fri Mar 07, 2014 11:45 pm 
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If it was a scope you might, it's a wide screen holosight.... The muzzle jump is, let's just say, significant....

Bob

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Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since!
Airsonal;
Too many! Springers, Pumpers, CO2, but I love my PCPs and developing them!
Proud Member of the 2000+fps Club!


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PostPosted: Fri Mar 07, 2014 11:48 pm 
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It's a shame you're so far away Bob, I'd sure love to see this pistol in action!


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