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Spring Piston Rifle

This area is for the discussion of BB or airsoft sub machine guns, and or other small arms such as pellets.
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Unread postAuthor: DerpWithAGun » Fri Dec 23, 2011 9:07 pm

@BTB hahaha great minds think alike! Don't worry I wont use idea of the pumping method using the stock, that kind of design is too complicated for me anyway. As for bolt action and revolving magazine, maybe, maybe not. The mechanism for making the magazine revolve will probably be too hard or not very compact.

@Zeus Of course I will put the hammer valve inside the pressure chamber. That was my plan from the start. But with the removable air cylinders and stuff I probably wont. That is too complicated for me. Having it all seal up 100% will be very time consuming and frustrating.

I was just wondering, would anyone be able to identify the name of this air rifle? http://sportsmk.co.uk/images/big/362.jpg I really like the way the pressure chamber is set up and I might go with this sort of design.

Also, this pneumatic target pistol: http://www.youtube.com/watch?v=Dp9LZLH3Kwg This is just like Crosman air pistol that JSR posted above except you pump the air into it by lifting the top of the gun. I would really like to know how this gun can shoot a pellet at such a high velocity by only pumping the gun up once, then loading a pellet in. And this gun isn't a springer because you can pump the gun up to 3 times at once and the pellet will shoot further and faster.

I would actually love a design like that. except my gun will be bolt action and you pull the bolt back really far, load a pellet into the barrel and then as the push the bolt forward again it pumps air into the very small pressure chamber. Someone please tell me this is possible! :D
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Unread postAuthor: Gippeto » Sat Dec 24, 2011 2:37 am

The rifle is the "venerable" QB 78...XS78 in the Uk.

Readily available, inexpensive, made from metal and wood, and modable out the wazoo. :twisted: Holds two 12gram co2 cartridges in the tube.

Qb79 takes paintball tanks. :)

Image


I would actually love a design like that. except my gun will be bolt action and you pull the bolt back really far, load a pellet into the barrel and then as the push the bolt forward again it pumps air into the very small pressure chamber. Someone please tell me this is possible!


Think about swept volume, and the amount of force you'll be able to generate with this design....you won't get diddly squat for pressure if you have a useful volume....it simply won't work.
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Unread postAuthor: jackssmirkingrevenge » Sat Dec 24, 2011 3:24 am

Very nice, is that a Ninja 13ci? :D

How did you cut the threads for the bottle?
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Unread postAuthor: Gippeto » Sat Dec 24, 2011 3:40 am

Ninja tank yes...re-ranged to 1450psi.

Tank mount block was done by a previous owner. Would cut the threads with a boring bar in the lathe.
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Unread postAuthor: DerpWithAGun » Sat Dec 24, 2011 5:04 pm

Okay, just going to go with this http://www.ebay.com/itm/Benjamin-Hand-P ... 3f08a2de90 and this http://www.ebay.com/itm/G7-paintball-re ... 27c1932679. Gonna put 2500 psi in this gun, 60cm long pressure chamber, 24mm OD chamber, bolt action loads the bullet and cocks the hammer. Done, simple as ever!

Thanks guys for the help, I'll post a new thread in the showcase part of this forum when it's done!
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Unread postAuthor: Mr.Sandman » Sat Dec 24, 2011 5:32 pm

I'm rather alarmed that you figured 2500 psi in tubing with 2 mm wall thickness was fine. It's good to see that you're trying something new, but do you have any experience with machine tools? It's not something you can just do, you have to know how to use them first, I'd recommend you practice making small things before attempting such a serious project.
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Unread postAuthor: DerpWithAGun » Sun Dec 25, 2011 12:12 am

Thanks Sandman, JSR recommend I build a pen gun first using the tutorial on this forum so I can get familiar with the tools. My Dad knows how to use the lathe anyway so he can help me a little. If 2mm is not enough then what do you think is safe? I still need threads so it would have to be pretty thick maybe 4mm or 5mm?
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Unread postAuthor: Mr.Sandman » Sun Dec 25, 2011 2:06 am

Well before anything, what material will it be made of? Aluminium, Steel, Titanium? Osmium? :lol:
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Unread postAuthor: DerpWithAGun » Sun Dec 25, 2011 6:18 am

Most parts will be steel and some parts that are not under pressure will be brass just for good looks. If it's too expensive for brass, pressure chamber, valve and any other part that is under pressure will be steel, the hammer, bolt and barrel will be aluminum.

If I get time I'll probably heat the pressure chamber in some hot coals until it is red hot and harden it. Unless the shop sells already hardened steel for cheap then I'll get that. Hardened steel might actually be too hard for the lathe to cut.
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Unread postAuthor: wyz2285 » Sun Dec 25, 2011 10:14 am

bolt action loads the bullet and cocks the hammer

May not be that simple as it sounds, you are going to use 2500 psi right? So what´s the valve sealing surface area? If it´s somewhere around 5mm dia, you will need a decent force hammer to open it, so recock the hammer with a linear action bolt may not be easy, at least in my experience, but I don´t know exactly what design you have in mind to connect reload with recocking hammer :roll:
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Unread postAuthor: Mr.Sandman » Sun Dec 25, 2011 11:16 am

DerpWithAGun wrote:If I get time I'll probably heat the pressure chamber in some hot coals until it is red hot and harden it. Unless the shop sells already hardened steel for cheap then I'll get that. Hardened steel might actually be too hard for the lathe to cut.

Why would you heat treat a pressure chamber? You're not making a knife, your making an air rifle. I think you might want to read up a little more on how air rifles are made.
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Unread postAuthor: Brian the brain » Sun Dec 25, 2011 2:03 pm

And please make tha bolt out of steel.
I threw away the aluminium one as it wore pretty fast.
It looked aweful in no time.
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Gun Freak wrote:
Oh my friggin god stop being so awesome, that thing is pure kick ass. Most innovative and creative pneumatic that the files have ever come by!

Can't ask for a better compliment!!
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Unread postAuthor: Gippeto » Mon Dec 26, 2011 11:54 pm

Mr.Sandman wrote: I think you might want to read up a little more on how air rifles are made.


X2...and the materials they're made from as well. :wink:
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Unread postAuthor: CpTn_lAw » Tue Dec 27, 2011 6:16 am

You need to do something : quit pretending you already know about stuff you clearly fail to understand. I'm being harsh, but we don't want to see you get harmed.
Advice here is free, people share their experiences and experiments, that includes self-criticism, and lucid look over past mistakes and successes.

There is no stupid question here, and most of the participants will gladly take a look at diagrams, questions of all sorts and guide you to a better understanding.

Your project is to my opinion a bit difficult. Gippeto built a fantastic piston rifle you should check out, BTB built several awesome looking and functional hammer valved rifles, operating at high pressure.

You should try to build something easier at first and gain experience by doing so. You will find that stuff you thought easy were tricky in reality.


Again sorry for being harsh, and feel free to question about anything you possibly want to ask, we will try to answer the best we can.

Be safe.
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Unread postAuthor: Brian the brain » Tue Dec 27, 2011 10:48 am

Without trying to contradict the above post I feel I have to say something after reading my own comment again.

Don't worry I wont use idea of the pumping method using the stock


When you gain experience I hope you do try it.

You just proposed 2 of the ideas I have been working on lately wich was a funny coincedence.

Everybody is welcome to use my ideas or to prove me wrong about them...improve on them, whatever.
If I wanted to keep them to myself I wouldn't post anything here...

But back to experience: I'm not sure I can pull off those designs myself.
I remember the days I just couldn't grasp the concept of a piston valve.
Experience comes through doing it.
This is how I learned not to trust a commercial checkvalve at 80 bar..at the expense of my upper jaw, my gums and my lip.
All healed up pretty well.

I also learned that, even in summertime, a PVC cannon can explode because of ice-ammo.
Cut my finger to the bone and BADLY bruised my upper leg.
The remainder of the valve missed my brothers head by an inch.

I would trade the experience in this case for good advice in advance if I could.
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Gun Freak wrote:
Oh my friggin god stop being so awesome, that thing is pure kick ass. Most innovative and creative pneumatic that the files have ever come by!

Can't ask for a better compliment!!
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