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Pistol build |
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Pauly5
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Joined: 11 Mar 2013 Location: Titahi Bay Status: Offline Posts: 1676 |
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Topic: Pistol buildPosted: 12 Oct 2023 at 3:55am |
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Over the past couple of months I have been inspired to build a pcp pistol. I do plan to build a breech, but at this stage I am basically converting a Crosman 22XX from CO2 to HPA using the trigger frame and steel breech.
Inspiration to do this is from a couple of very clever people that have given me good advise and the recent purchase of a small vertical mill has rocketed my confidence in build quality. This won't be a long thread, but you should get the general idea of what i've done. I started looking at other designs in both the big bore and lower power design. The possibilities and concepts rattled around my brain for a while and I started off planning to use the std valve system that came in the 22XX. I ended up using a bigger sized tube, and so I had to make my own valve and hammer system. My main concern in all of this was safety. So after getting all the info together I felt good about what I was to do with a 3 x safety factor for retaining the pressure. With this sorted it gave me a base to work off. I didn't know what sort of performance the pistol would produce, but I have been pleasantly surprised and now have a base to work off for future build and refinements. Photos show a few different stages including my trial and error parts. I basically built the pistol twice. This was a good idea as it meant the finished item had minimal adjustments made to it, and my measurements are recorded, so each build will be quicker. Photo to come in another post. Thought i'd get the words done and dusted first. I will also share a bit more detail about it's performance too.
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Pauly5
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Posted: 12 Oct 2023 at 4:05am |
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J-S
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Joined: 20 Oct 2014 Location: Auckland Status: Offline Posts: 497 |
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Posted: 12 Oct 2023 at 5:56am |
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Pretty bloody cool.. |
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J S Airguns
Air Arms TX200('s) Theoben Sirocco HW77 FWB 300s Webley Patriot One or two others... Current projects: Too many.. |
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Pauly5
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Posted: 13 Oct 2023 at 4:27am |
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So my first fill was around 1800 psi and I shot it down to around 800 psi.
I used JSB 18.13 grn pellets. 33 usable shots and quite a gentle power curve. The variation between shots jumped about, but as I was shooting this string I was shooting groups and on paper it was a dead rabbit every shot. Hopefully in the future I can refine this with trialing different spring tension and addition of a hammer tension adjuster to balance the valve and hammer. Shot string copied below.
I'm not after perfection, and to me it's a victory so far enjoying shooting it. I have teamed this up with a cheap hand pump and it only takes 50 strokes to fill to around 1800 psi according to the gauge on the pump. It's turning out to be a good little combo. |
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kruzaroad
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Joined: 03 Jul 2022 Location: Hastings 4 now Status: Online Posts: 2694 |
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Posted: 13 Oct 2023 at 11:13am |
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Looks awsome.
Why did it take 9 shots to hit the 600fps mark? Ave for first 9 shots = 578 fps Ave for next 17 shots at (600fps +) = 658 fps. Thats a 80fps gain. Like wise the last 6 shots Ave =571 fpe (no calculated decimals but was 571.5) Is a 87 fps drop. The drop off at the end I understand. The ones at front I don't. If it's just it needed time to settle in I'd say you'd be closer to 650fps. |
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Pauly5
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Posted: 13 Oct 2023 at 12:25pm |
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What the numbers show is typical of a non regulated pcp. Also called the power curve. That's what the grapgh shows. A regulated shot string is in theory a flat line until it drops below the reg pressure,
What is happening there is that the tank pressure (1800) is a littler bit stronger than what the current valve/hammer set up can use, so it isn't hitting hard enough to release full energy. Once a few shots are fired and the pressure drops, the hammer can open the valve longer giving a higher pellet speed. So if I filled the tank to say 2500 psi, it would likely have even lower initial speeds. If I want to utillize higher tank pressure I will need a stronger hammer tension. This tank is quite small, so I feel that to get 30 + good shots means I have been lucky with this setup. The variation in the spread between shots can probably be reduced with refining of the firing parts. |
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kruzaroad
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Posted: 13 Oct 2023 at 12:35pm |
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OK that makes sence.
Do you have stronger hammer springs? I got a few when I got them made up for 362. Didn't use the strongest. Still have 3 i think of differnt strengths. Let me know if you have trouble finding any. |
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Pauly5
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Posted: 13 Oct 2023 at 1:09pm |
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I plan to get some, but I can also put an adjuster in to create more tension. The more power I get, the less number of useful shots, but it's a case of seeing what happens.
Lots of avenues to develop. |
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kruzaroad
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Posted: 14 Oct 2023 at 1:39am |
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So what's the weight of the pistol?
And where is its point of balance? The hammer spring tensioner sounds like good idea. Not only as you could increase the tension but you could reduce it for indoor/around structors bird shooting. Which I imagine would be a bonus in your line of work. Be keen to see a review of your mill at some stage too, if your keen. |
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RangerPete
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Posted: 14 Oct 2023 at 7:06am |
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Pauly, what about fitting a reg, like the huma you put in my little Elly?
That should flatten out your power curve nicely, maybe even give you a few more shots.
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Walk quietly, but carry a big stick.
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Pauly5
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Posted: 14 Oct 2023 at 9:44am |
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Yes, it's a possibility for sure. On another build I can make the tank bigger so that there's more room for a reg and air. It will probably suit a carbine style gun with the bigger tank, as it will be kinda big for a pistol, although Dirty Harry had no problem wielding his pistol. |
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Pauly5
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Posted: 15 Oct 2023 at 8:17am |
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What a disgusting day outside here in Wgtn. So into the garage I go.
I had a slow leak from the valve, so I have made a new poppet out of a softer material in the hope it will seal easier under pressure. Time will tell, but it is holding so far. I also made a seat/spacer for the hammer spring and this forms part of the adjuster. Pretty basic, and i'm sure there are better looking ways to do this, but function first right? ![]() You may also notice different grips. I am now using the std Crosman grip frame and some nice grips made by a great craftsman that inspired this build. So I pumped it up to 1800 psi and the first shot using 18 grn JSB was around 13 fpe, which was a good 3 fpe gain with the spacer. I turned the adjuster a couple of turns and got just over 16 fpe. I'm pretty pleased with that, as it's a good little hunter with that power, without being too loud. The silencer can certainly be made better as it is the one off my 362. The next 6 shots were all in the 16 fpe mark before dropping under. I also tried a red dot sight I had. I'll see how it feels using it, and it is lighter. Kruz, I haven't weighed it yet. It's heavier than a 2240, but it's a nice weight. The centre of G is around the front of the trigger. I will shoot a string later. I am expecting less shots of course, but the numbers will tell. Consistancy is what i'm after |
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RangerPete
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Posted: 15 Oct 2023 at 9:47am |
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Nice.
Whats the barrel length and over all length? And how do you fill the tank?
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Walk quietly, but carry a big stick.
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Pauly5
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Posted: 15 Oct 2023 at 10:44am |
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Pistol is 450 mm without silencer.
Barrel is 350 mm long. I made the fill valve to fit an 8 mm fill probe, so it fills exactly like your S510. I have been using a hand pump. Basically 50 strokes from empty and i'm at 1800 psi according to the pump dial. I have another barrel that I will use to make a shorter pistol with the barrel the same length as the tank.
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nunga
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Posted: 16 Oct 2023 at 1:02pm |
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Thats pretty cool. makes me want to get that .25 barrel i have and make one as well. But i have way too much on my plate right now but hopefully the next couple of months and i might have some free time.
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2nd place HP springer - WFTF World Championships 2014
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