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 Post subject: .22XX PCP
PostPosted: Fri May 01, 2009 10:05 pm 
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Location: Coalmont BC
I've been quietly working on this project since Christmas, and finally got to shoot it today.... Based on a 22XX tube, it has a Discovery valve (exhaust port corner rounded) bolted to a QB79 tank block.... Only the tank block and the valve are pressurized (O-ring between).... but both are bolted into the tube for extra security.... The tank is a 9 oz. CO2 tank, which is rated at 1800 psi.... At the moment it has a 14" barrel in .22 cal.... more to show just how compact it is, and to find out what kind of performance I can get out of a PCP Carbine.... :twisted:

Image

I started out at 500 psi to make sure I could take the tank off under pressure (no problem, the QB79 block vents perfectly).... Then shot a few shots at 1000, 1200, more at 1400, even more at 1600, and then a full string at 1800.... Using my Disco pump, it takes 20 pumps per 100 psi, so it's 360 pumps from empty to 1800.... but you only have to do that once.... :roll: .... basically you get a shot for every 2 pumps, which I think is pretty cool.... 8)

Image

The first short strings, I only shot down to 98% of the peak (starting) velocity, but the 1600 and 1800 psi strings I shot down to 96% of peak.... That gave the following results, using JSB Espress 14.3 gr pellets:

Starting Pressure; Average Velocity; Number of shots over 98%; Number of shots over 96%

1000 psi; 671 fps; 6 shots
1200 psi; 712 fps; 7 shots
1400 psi; 747 fps; 10 shots
1600 psi; 771 fps; 15 shots; 26 shots
1800 psi; 771 fps; 29 shots; 47 shots

As you can see, pumping to 1800 psi gives nearly 50 shots within a 30 fps range by shooting down to 1350 psi.... It would require about 100 pumps to refill.... If you start at about 1750 psi and shoot down to 1450 you can get over 30 shots within a 20 fps range and it will take about 70 pumps to refill.... :shock:

I'm only just starting to play with this platform.... at the moment it has a stock transfer port (0.140").... so although the barrel port and valve are relieved somewhat, the gun is restricted to resemble a stock Discovery at the moment.... I did try it with a 24" barrel, charged to 1600 psi.... It acted quite differently with the longer barrel, with the shot string starting out at about 805 fps, peaking at 828, and dropping back to 800 at about shot 45 (1150 psi).... This is a flatter string than a stock Discovery, and nearly twice as long.... :shock: .... My stock Disco (charged to 2000 psi) with the same pellets started at 800 fps, peaked at 838, and fell back to 800 at shot 24.... Since the 24" barrel has about a 50 fps advantage over the 14" barrel, I think I'll do the rest of my development work with the longer barrel.... That will allow direct comparisons with the Discovery, just for giggles.... :lol:

Next step will be a larger transfer port.... and some playing around with the velocity adjuster.... Waiting in the wings is a JDS Airman 13 cu.in. tank with a 1600 psi regulator.... I have my PAL, and the finished product will, of course, be registered.... :twisted:

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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 Post subject: Re: .22XX PCP
PostPosted: Fri May 01, 2009 11:59 pm 
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Location: Tecumseh
its been quite awhile since ive seen such a good write up/charts/ and numbers with a 22xx series. especially with such a heavy mod. the numbers look good a 2240 spittin lead at 800 fps is very nice indeed. what kind of pellets are you using to get those numbers?

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 Post subject: Re: .22XX PCP
PostPosted: Sat May 02, 2009 9:40 am 
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Location: Coalmont BC
JSB Express 14.3 gr.... 770 fps average w/ 14" barrel.... 820 fps average w/ 24" barrel.... with stock transfer port....

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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 Post subject: Re: .22XX PCP
PostPosted: Sat May 02, 2009 9:52 am 
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Location: Tecumseh
rsterne wrote:
JSB Express 14.3 gr.... 770 fps average w/ 14" barrel.... 820 fps average w/ 24" barrel.... with stock transfer port....

Bob


ide take a guess if u open that up a bit more should yeild around 20 fps ish...
thats what i got around with my 2289. but were also dealing with a bulk air here, so u may get a little more.

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 Post subject: Re: .22XX PCP
PostPosted: Sat May 02, 2009 10:00 am 
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Location: Coalmont BC
I gained about 30-40 fps on the Disco with a 0.160" transfer port....

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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 Post subject: Re: .22XX PCP
PostPosted: Sat May 02, 2009 5:52 pm 
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Joined: Sun Apr 05, 2009 1:16 pm
Posts: 81
Location: PortColborne/Wainfleet Border
why would you register a 2240 ? I can't see why anybody would even bother?. just tinker around with it and keep it to yourself, no need to bring airgun modifications to the cfc's attention.


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 Post subject: Re: .22XX PCP
PostPosted: Sat May 02, 2009 9:47 pm 
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Location: Coalmont BC
Actually, you can't register a 2240, AFAIK.... You can (and must) register a 2250, and that is what I will be doing.... As far as why?.... I have my PAL, and don't want to break the law.... I have done this before.... :roll:

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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 Post subject: Re: .22XX PCP
PostPosted: Sat May 02, 2009 10:37 pm 
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Location: Coalmont BC
I drilled out the transfer port today to 0.159".... and shot some strings with various hammer spring settings.... The number of turns "out" is measured from coil bind using a Discovery hammer spring.... All testing was done with JSB Express 14.3 gr pellets and the 24" barrel:

Image

As you can see, at 5 turns out, the 96% shot string starts at about 1700 psi, peaks at about 1350 psi, and goes down to about 1100 psi.... the 4 turn string starts at 1800 psi, peaks at about 1500 psi, and goes down to about 1300 psi.... The 3 turn string is already on the sweet spot at 1800 psi, peaks at about 1650 psi, and goes down to about 1400 psi.... The 2 turn string is starting from the peak velocity at 1800 psi and ends at about 1500 psi.... Here is a summary of the results:

Setting; Average velocity; Energy; Shots within 98%; Shots within 96%; Pumps to refill:

5 turns; 822 fps; 21.5 FPE; 42 shots; 64 shots; 120 pumps (to 1700)
4 turns; 858 fps; 23.4 FPE; 36 shots; 52 shots; 100 pumps (to 1800)
3 turns; 884 fps; 24.8 FPE; 30 shots; 36 shots; 80 pumps (to 1800)
2 turns; 911 fps; 26.4 FPE; 13 shots; 22 shots; 60 pumps (to 1800)

It seems to me that the best setting with this setup would be about 3 1/3 turns out.... I didn't shoot a string that way (yet), but it should start at the beginning of the 98% sweet spot (at about 863 fps), peak at about 880 fps, and produce about 32 shots between those numbers.... with an average velocity of about 872 fps (just over 24 FPE).... If you find the 96% curve acceptable, then the 4 turns out curve is perfect as is.... 8)

I am very pleased with this platform so far.... It is capable of over 900 fps with standard pellets.... or it can shoot more than 50 shots at between 832 and 867 fps.... It looks like with the 1600 psi regulated bottle, I can expect to be able to adjust the velocity between about 800 and 900 fps.... :twisted:

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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 Post subject: Re: .22XX PCP
PostPosted: Sun May 03, 2009 10:43 pm 
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Location: Coalmont BC
Just fine tuning today.... drilled the barrel port out to 0.166" (#19 drill) and the transfer port out to 0.161" (#20 drill).... I also extended the bolt probe by 0.150" and shortened the back of the bolt by 0.060" (to allow more room to load pellets with the longer probe).... Those mods didn't affect the velocity any significant amount, but they changed the shape of the curve a bit.... I tested this version with five different pellets: 11.9 gr. RWS Hobby, 14.3 gr. JSB Express, 15.9 gr. JSB Exact, 18.0 gr. JSB Heavy, and 21.6 gr. Kodiak (all weighed).... The pressure curve is close enough to the same for all pellets, so I only show one on the graph.... The tank was pumped to 1800 psi, and I ended the shot string when the velocity dropped to 96% of the maximum for that pellet.... I had the velocity adjuster set 3 turns out from coil bind with the Discovery hammer spring for all testing....

Image

As you can see, the Hobbies had lots of velocity, but a much shorter shot string.... as the pellet weight increased, you got more usuable shots, more FPE per shot, and the total energy in the usuable string increased as well.... Here is the summary:

Pellet; Average velocity; Energy; Shots within 98%; Shots within 96%; Total Energy within 98%

Hobby; 956 fps; 24.2 FPE; 18 shots; 30 shots; 435 FPE
Express; 884 fps; 24.8 FPE; 32 shots; 41 shots; 795 FPE
Exact; 849 fps; 25.5 FPE; 33 shots; 40 shots; 840 FPE
Heavy; 806 fps; 26.0 FPE; 35 shots; 44 shots; 909 FPE
Kodiak; 736 fps; 26.0 FPE; 42 shots; 50 shots; 1092 FPE

My conclusions are that the Hobbies are too light and the Kodiaks are too heavy for this gun.... The Kodiaks have a lovely long shot string, but don't have any more energy per shot than the JSB Heavies and a lot less velocity.... I kind of expected this, but it's nice to have the numbers to look at.... If I were doing a .177 version of this gun, pellets of over 10 grains would probably produced great results for FT work.... :twisted:

I think I've pretty well figured out this version.... so the next step is to try the 3000 psi JDS 13 cu.in. tank with the 1600 psi regulator.... It looks like 1600 psi is right in the middle of the sweet spot for all pellets except the Hobbies.... so I guessed right when I bought the regulator, anyway.... :roll:

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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 Post subject: Re: .22XX PCP
PostPosted: Tue May 05, 2009 10:16 pm 
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Location: Coalmont BC
I've been impatiently waiting to get to this stage.... I fitted the JDS Airman 13 cu.in. bottle today.... 3000 psi regulated down to 1600 psi.... It's lighter than the 9 oz. CO2 tank, and the complete gun weighs in at an ultralight 4 1/4 lbs.... :shock:

Image

The gun balances beautifully.... about 2 inches in front of the trigger guard (ie further back than my Disco).... and it's very comfortable using the tank as a foregrip.... :wink:

It took 305 pumps to fill the tank to 3000 psi from empty, and the Disco pump worked prefectly.... I let the gun cool for a half hour, and lost about 100 psi, so the string started from 2900 psi.... I shot 20 shots with JSB Express 14.3 gr, and the total variation was only 8 fps.... tons of pressure remaining, so I shot 10 JSB Exact 15.9 gr and then another 5 Express.... Still lots of pressure left, so I did 10 shots with JSB Exact Heavy 18.0 gr, and then another 5 Express.... This brought me up to 50 shots, and I was only down to 1900 psi... I shot three shots groups playing with the velocity adjuster, from coil bind to 8 turns out, and then a final 3 shots back at my initial setting of 3 turns out.... The pressure was down to 1500 psi, but the Express were still shooting within 20 fps of the highest.... This was after a total of 78 shots.... :shock:

Image

The graph above shows the first 60 shots with the 1600 psi regulated setup, adjuster at 3 turns out from coil bind.... I left the curves for the unregulated setup with the same three pellets there for comparison:

JSB Express 14.3 gr averaging 876 fps - 24.4 FPE
JSB Exact 15.9 gr averaging 843 fps - 25.1 FPE
JSB Heavy 18.0 gr aberaging 794 fps - 25.2 FPE

All shots for each pellet were within 1% of each other in velocity.... so the regulator is DEFINITELY to way to go for consistency, compared to the unregulated setup.... The pressure drop in the tank with the adjuster at 3 turns out was almost exactly 20 psi per shot.... so from 3000 psi down to 1600 psi that means a completely flat 70 shot string.... :shock:

Image

The second graph shows what effect the velocity adjuster has.... First of all, note that I can get about another 10 fps by cranking the adjuster in one more turn (to 2 turns out).... but after that there is virtually no increase.... My guess is that it would take a larger valve volume to take advantage of the increased lift/dwell of even heavier hammer strikes.... Basically, the gun is dumping all the available air in the valve at 2 turns out.... As you decrease the hammer spring tension from there, however, the velocity goes down, and the gun get progressively quieter, until it eventually becomes quite a "clipped" pop.... presumably at a much higher shot count.... just the ticket for plinking.... I have no idea how long the shot string might be at the lower velocities, but it would be loonnnggggggggg.... 8)

To say I'm delighted with the results would be an understatement.... I'll be doing a bit of fine tuning, to be sure, maybe take a couple of threads off inside the valve, play with the porting a bit more.... and optimize the velocity adjuster to get the most velocity without shortening the shot string too much.... The gun will get a scope, and possibly a "Packhunter" stock from sniper.... and likely a barrel band at the front of the tank.... but just the way it is , I have a gun that will fling 14.3 gr pellets downrange at 876 fps, and deliver 70 shots from 140 pumps to top the tank back up from 1600 psi to 3000 psi.... :twisted:

The unregulated version has its advantages too.... only an 1800 psi fill, shoot it down to 1400 psi, get 30-35 shots within 2% of each other.... and you only have about 70 easy pumps to refill.... In addition, you can change the bottles without removing the barrel, so you can carry a spare, and they are a lot cheaper.... Either version looks like a winner to me.... 8)

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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 Post subject: Re: .22XX PCP
PostPosted: Wed May 06, 2009 12:05 am 
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Good work on your new rifle.Very light, lots of power, a real good combo. A rifle you can carry in the bush all day long. Great idea you had Bob. I see one in the near future. Benson.


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 Post subject: Re: .22XX PCP
PostPosted: Fri May 08, 2009 1:57 pm 
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Location: Coalmont BC
For those of you who care.... I found out today that what I thought was coil bind on the Disco hammer spring in this gun was 1 turn out from coil bind.... The shoulder on the adjuster was hitting a bolt, rather than the spring bottoming.... I modified the adjuster to allow me to reach coil bind.... so all the adjuster settings above this post are wrong by one turn.... ie if it says "4 turns out" it is actually "5 turns out".... From this post on, the adjuster settings will be correct.... :oops:

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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 Post subject: Re: .22XX PCP
PostPosted: Fri May 08, 2009 11:24 pm 
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Location: Winnipeg, Canada
How well are your valve stems standing up to that discovery spring? It looks like you've been shooting enough with this spring to notice anything "un-toward"....

Regards,

Doc Sharptail

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 Post subject: Re: .22XX PCP
PostPosted: Sat May 09, 2009 2:57 am 
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rsterne wrote:
From this post on, the adjuster settings will be correct.... :oops:


I assume you will be banning yourself voluntarily from the forums for 3 weeks, plus one day for this infraction.

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 Post subject: Re: .22XX PCP
PostPosted: Sat May 09, 2009 8:42 pm 
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Location: Coalmont BC
I haven't noticed any problems with valve stems using the Disco spring.... mind you this gun has a Disco valve too.... :lol:

I was running a 2200 spring in my Uber-Pumper cranked to the max with no problems.... the Disco spring is probably only 25% stiffer, and most of the time I don't run it near coil bind....

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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