Spring Piston Rifle

[CpTn_lAw]

Your last design could probably -if changed a bit- work. what is your chamber cross section? At 1000 psi, you will need a small valve seal diameter.
But I still feel uncomfortable with your posts. You know that what you are searching for is actually really simple to build if you choose your parts correctly and do some elementary calculations?
As for epoxy, JSR is the master in that area, but uses it to secure pieces together, not to make end caps. (Or at least he doesn't anymore, the endcaps failed at 850 psi IIRC)

I understand you are trying to make a badass pneumatic rifle that would level out the commercial ones... But trust us on the subject.
There are no shortcuts, everyone has to learn the basics and experiment safely.

[DerpWithAGun]

"1000psi held in by some epoxy" JSR told me it was possible, I just confirming it on this thread. If you want proof read on this thread: http://www.spudfiles.com/forums/cartrid ... 23608.html. You calling JSR a liar?

"try joining the Army Cadets with a criminal record thanks to your "magic" gun." Sorry forgot to mention, Uncle has a farm, I'm not as stupid as you think I am, why the hell would shoot a magic gun in my backyard? Air guns are just as illegal so why don't you try stop me from making an airgun?

"heat treated pressure chamber" Sorry there has been a miss-understanding. I have worked with and know quite a lot about the construction of certain magic guns. Most magic guns need most parts heat treated. Due to the similarity with air guns and magic guns, I have slightly been confused.

I've made a QEV already. Too loud and I find it quite unpleasant to be pumping air after every shot. I made one with 300 psi in it. Borrowed a friend's compressor. My old QEV is long gone, dismantled into a hundred pieces because it was so loud.

What does "go and play Xbox for a while and LOL while ROFLMAO." mean? In my opinion that was pretty lame. I play Xbox simply because it is fun and kills time when I'm bored. Have a problem with that? Don't mistake me for some CoD fanboy who thinks he knows everything about military guns. I have never owned a single CoD game.

@CpTn_LAw What do you mean by chamber cross section? My deisgn that I have posted is only a rough concept of what I am aiming for in the final product. For example: The valve stem housing will be significantly shorter due to the large amount of dead volume. Final and precise calculations haven't been done but will eventually be done. Of course I trust what you are saying, after all your the expert and I'm not. I'm slightly doubting the idea of epoxy plugs. I just hope that drill bits for making threads aren't expensive. The only things that will be threaded is just the pressure chamber and every single part that is under pressure. Parts such as the barrel, an end plug for the striker and the area where the spring holds the valve shut will be epoxied in place.

The valve stem will be 2mm thick and hopefully made of titanium for strength. The valve seat, well this is my first PCP so I don't know what would be the best size for it. I will probably make the valve housing out of delrin or another soft plastic so that it can seal better.
I'm looking for the strongest, cheapest and most efficient design I can get. Hence. where the epoxy idea originated. Thanks for the help and concern CpTn_LAw!

[CpTn_lAw]

I mean easy calculation can be done. By cross section, i mean: you use a cylindrical chamber, then what is 'pi * r^2' ? (r being the radius of the pipe)

From there you can calculate the force pushing the valve to seal. and from there you can calculate how much energy your hammer has to transfer to the valve stem to open it up sufficiently to get an efficient shot. (efficient being defined by your terms, "number of shots, power etc...")
I suggest you also do some research about the strength of the pipe you will be using as chamber/valve/barrel.
1000 psi is nothing to fool around with. And btw, multishots are possible with QEV's and small volumes. The fact that they are not all that simple is irrelevant here considering the trouble you're going through to make a PCP.

Also, to work with titanium, you will need "fairly solid" tools.


And last but not least:
What evilvet is trying to say is exactly what he said. To many people tend to get excited and get in a project they don't even begin to understand. The gas ram in the first pages was a perfect example of what i'm saying. So bear in mind that seing all sorts of stuff around here we can be and certainly are scpetic when people arise from the dark and say:
"yay, me wanna make big multishot pnoob with 1000 psi foot pump compressor using diamond as main material. Do you think wet bread make good sealant? "

keep safe and do some research about materials.

[DerpWithAGun]

I'm not really that excited. I fully understand the concept of a PCP rifle but I do not have enough knowledge about materials and construction. That is why I am here asking.

About that titanium.. well I won't be doing too much work on it. Valve stem design will be pretty basic. Only the valve stem will be made of titanium. I'm going to go with a full steel construction. Barrel will be steel, 1/2" size and will have a 4.5mm insert for .177 pellet or a BB. I might make the bolt out of brass because it could look better but that is not necessary. I was also looking at this: This guy's PCP is only 100 psi and can take out pigeons so it must have a pretty high FPS. I would be happy with something like this except I would make a machined version, a lot more compact and neat. This gun shoots 3mm BB and that wouldn't be a problem, I wouldn't mind firing 3mm BB as long as it is accurate at 15m minimum. He gets quite a few shots with only 100psi. I wonder how?

I've spent a month now thinking and researching all the different types of air guns and finally chose to make a PCP. I choose PCP simply because I hate pumping up after every shot. I have spent a long time doing research and designing. I am certainly not rushing into this project. That's the last thing I want to do.

I haven't even got my lathe and mill yet. It has been very hot in Australia right now over 40 degrees and my dad told me he will only buy the machinery if I help him clean the area to make a new workshop. It's been too hot to work on it he said.

Trust me, I will be safe, I'm not an idiot.

[CpTn_lAw]

High FPS doesn't mean anything...
You could shoot a 0.01 mm pin at 5000 fps and wouldn't get much damage (if it's what you seek.) Also try not to talk about shooting living stuff.... it's in the rules.
Accuracy is very relative aswell. What sort of grouping do you want? 1" at 15 meters? 1/2" ?
All these characteristics need to be well thought if you want to build the said PCP rifle.

[DerpWithAGun]

Sorry about the animal thing, I just used that as an example to show that this gun has some pretty decent power. I would want at least 2" groupings at 15m. I'm not too fussed about the power. All I want is range, accuracy and a high FPS, muzzle velocity I'm not too fussed about. I just want to be able to use this and have fun with friends shooting cans off the fence and practicing my target shooting skills.

[CpTn_lAw]

Sorry about the animal thing, I just used that as an example to show that this gun has some pretty decent power. I would want at least 2" groupings at 15m. I'm not too fussed about the power. All I want is range, accuracy and a high FPS, muzzle velocity I'm not too fussed about. I just want to be able to use this and have fun with friends shooting cans off the fence and practicing my target shooting skills.

You see, that's what makes me sceptic. FPS = Feet Per Second, your projectile has to come from somewhere (i.e. your muzzle end). It won't accelerate by itself after it leaves the muzzle. You kinda contractict yourself here.

Range will come mainly from the projectile's weight, shape, size, initial velocity. See in my hybrid, i can shoot a 2 gram fruit/ projectile at 600 m/s but it will fly less than 100 m and even if the hybrid is in a vise, i won't be able to get 10" groupings at 15m.
However, shooting a 200 grains lead ball saboted at 280 m/s, the range will be...somewhere around a mile maybe at the most optimistic scenario, but the groupings...less than an inch at 15m.

So, let's be honest, you want a multi shot precharged pneumatic rifle in .177 caliber, that shoots several shots above 700 Feet Per Second before pressure drops, and -letting your skills aside- that can group 2" at 15 m.

Be clear for yourself. Take the time, and not just "oh fun that sounds good what spudfiles member suggest" , sit, take a sheet of paper, a pencil and start tossing ideas on the paper, really think well about this.

[CooperJS]

Be clear for yourself. Take the time, and not just "oh fun that sounds good what spudfiles member suggest" , sit, take a sheet of paper, a pencil and start tossing ideas on the paper, really think well about this.

QUALITY QUOTE!!

[wyz2285]

This guy's PCP is only 100 psi and can take out pigeons so it must have a pretty high FPS.

I watched his videos too, 100 psi he said? well he could fake the video as he didn´t show how he killed the birds. And even he did, he could have done it with a very close distance, I see pigeons in my garden everyday, just about 5m away, you could shot one was a blowgun and a dart.
His gun is not very well made, there are quite a lot dead volume, so I did belive what he said

[DerpWithAGun]

Haha I did contradict myself there! It was late last night when I posted that and I was probably a little sleepy.

So, let's be honest, you want a multi shot precharged pneumatic rifle in .177 caliber, that shoots several shots above 700 Feet Per Second before pressure drops, and -letting your skills aside- that can group 2" at 15 m.

You speak the truth here, pretty much what I'm aiming for. Seriously, all I want is a really simple PCP that can do what you just said. wyz2285 said in an earlier post on page 3 that rifled barrels will make no difference to BB but rifling may help for lead pellets. If this is true then how can a commercial air gun be so accurate? I was just thinking, I could probably buy a .177 caliber barrel, rifled and all....

Also, one last thing, have you seen the Webley Alecto pneumatic pistol? It only takes 1 pump of this gun and you can shoot a pellet at a very long range, high FPS and accurate. Then you can pump it 3 times and you get the same thing but higher FPS and longer range. Can someone explain how that works? If I could understand how that works then I would build that. No need for stirrup pumps or Co2.

Once I'm 100% happy with the materials I'll use and what I'm aiming for then I'll sit down with pencil and paper.
Thanks.

[evilvet]

If I could understand how that works then I would build that

And that says it all........................

I understand how nuclear fission works, so I guess I'm all set then, world conquest here I come.

[CpTn_lAw]

Commercial guns are accurate when using some type of pellets. For example, i have a crosman 1377c stardard edition, no mods: it can shoot less than 1" groupings at 10 meters, holding it with one hand, match shooting stance with some good quality wadcutter pellets, but throw in some nasty beefy pellets and voilà : sauce spray party.

Now those commercial guns are typically more accurate because they are machined with the right tools. The twist rate of the barrel rifling is adequate to the advertised muzzle velocity of the projectile => the spin stabilization is effective and the pellet flies "straight" . (parabolic but hey you understand)

You could buy a crosman .177 or .22 rifled barrel for cheap on ebay or something like that and thread the end to accomodate your air rifle.

As for the workings of multi-pump pellet guns, i suggest you do a little research, the answers are on this very website.


But again, i think you are missing the point. Every one of us has thought about their spudguns, some have even invented new types of valves, designs, fueling methods, cartridges style, detent gun and so on... We can give you advices, answer your questions, but in the end you will have to build your PCP. I was saying you should sit down and think, that wasn't to think about new easy ways to obtain knowledge from us, that was to encourage your creativity and ingeniosity, maybe even come up with a design we havn't thought about.

You know these cereal boxes with cardboard stuff you can cut out and it says "ask a parent to help you with the cisors", well, our role is not to be parent, you do your part, show it to us and then we can think of ways to improve, not the other way around

Now the earth has rotated and it's time for me to go to sleep. Tomorrow : Computationnal fluid dynamics exam!
Have a nice day

[DerpWithAGun]

Alright, thanks for the helpful info!

I've decided to use an 88g Co2 cartridge as my pressure chamber. Found a cheap one on E-bay. JSR told me they are useful up to 1000 psi. Perfect for my project.

Going with the original idea of a PCP. Not going to do a multi stroke pneumatic. I read on the internet that they are very tiring to keep pumping the air in.

If I use a smooth bore barrel do you think BBs and pellets will still be accurate? I found a barrel on E-bay, 14.5 inch one that is cheap but is too short for my liking. Found a 24" which I'd be happy with but it is $50 and I don't have that kind of money to spare right now.

[jackssmirkingrevenge]

JSR told me they are useful up to 1000 psi

"JSR told me" should not be your safety standard, remember that JSR has had more than his fair of launchers blowing up but it's safe to assume that if something is rated for liquid CO₂ can safely take 1000 psi of air without coming close to failure.

You know these cereal boxes with cardboard stuff you can cut out and it says "ask a parent to help you with the scissors"

I have to say you're being very patient, almost like a parent

[DerpWithAGun]

What do you mean "very patient" JSR? Am I annoying everyone?

So you are saying the 88g Co2 cartridge isn't safe to use under 1000 psi? Why tell me in another thread that it is safe and now deny it?