Prototype Scoped Rifle (Piston actuated) (New info:23/06/11)

[Keringkien]

Hello everyone

This is a prototype of my first piston actuated air rifle, the photo's that you see here are what it looks like currently, I will update them as I go along. The parts were partially sourced from materials around my home and partially from Bunnings (I'm from Australia). It has approximately a 20mm bore which will be sleeved with (hopefully :p) a .22 rifled barrel.
UPDATE: I will be making a rifle similar to Vh_man's stick pneumatic's (Here). I will hopefully be able to get the parts within the next 2 weeks (dangnamit Australia!), I will be posting a video soon here too, of how the gun worked. (22/6/11)

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It is a bolt action (literaly, see the bolt in it :p, Photo 3), which works in the proper fashion, ie. only move the bolt not the barrel.

Chamber
The chamber is galvanised iron and is most likely going to be replaced in the future, in the 5th picture you can see the bottom piece of wood, (darker) the chamber could extend to that height and maybe be shortened to only have a slightly larger air capacity at my current pressure, (If I'm going outside away from my air compressor, I'll have to use a shock pump or something of the equivalent) this would mean that my final product will not use the wood shown in the pictures here (the current pictures, 20/06/11 - Aussie form), and perhaps something that would be a single piece stock of Australian hardwood or a tree of similar strength (suggestions please?).

Scope and action housing
The scope that you can see here (20/06/11), is for guessing purposes only, it doesn't actually line up correctly so you may be thinking "why have it?", I can assure you that having a slightly crooked sight is better then not when your aiming at a target 15m away (45ft), plus I didn't feel like making iron sights that obviously don't magnify at all. It is a Nikko 6x40 scope. The scope and action holding piece of wood (picture 5 20/06/11) is just a mock-up prototype of Cyprus, the final stock will consist of this component, the butt of the gun and maybe (depending on whether I enlarge the chamber or not) the front rest.

There is a slight problem with the piston seal which I think I can fix with a new rubber gasket. I am also thinking of adding a piece of tubing to link the tee with my blowgun to a better spot, perhaps under the chamber.

I appreciate you taking the time to read all that Please tell me what you think about the layout, remember this is just a prototype, and I would also appreciate a link to a topic for a proper, cleaner, bolt action assembly as mine leaks air when the blowgun is pulled. Thanks again,

Keringkien

Photo 1:

Photo 2:

Photo 3:

Photo 4:

Photo 5:
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[LovableAirGuns]

nice, that's looking great looking forward to a video and more guns from you

[Keringkien]

Thank-you very much for your reply I'm thinking of spending the next three the weeks working on this one, hopefully getting it to work accurately, then maybe I will make a few more, perhaps a semi-auto one.

[jackssmirkingrevenge]

10 points for effort and excellent write-up, I almost feel bad writing the following, please take it as constructive criticism:

- your pilot volume is far too big, I understand you are limited by standard parts but with some thought (and perhaps binary adhesive ) you can find ways around it. You could have a single schrader as filling and pilot valve with a simple trigger. Aside from power, you get the benefit of compactness and a more "realistic" appearance.

- a scope held by cable ties won't do, consider buying a couple of these - dirt cheap and will fit nicely around a sleeved barrel.

- for a small bore, high pressure is much more important than chamber volume. Unless you want a repeater, I would ensmallen (:roll:) the chamber to 1 or 2 cubic inches and use a shock pump to take it to 400 psi or so, you will appreciate the difference in power.

- if you don't have access to machining facilities, epoxy could also give you the opportunity to make a "proper" bolt action with o-ring seals, something like this:

[wyz2285]

jack I tried that bolt action! It doesn´t work !! once a miss load it stops reload completely all the air just come out from the front.

[Keringkien]

Thank-you very much for your input, I do appreciate it all I do notice that when it fires (very solidly I might add) that a lot of air air escapes out the pilot, When the piston was a little tighter (It's just a screw with tape around it at the moment) I could fire it with the schrader valve, which surprised me because it was a really simply made piston... Yes I do realise that the scope it terribly mounted it was just a simple and quick mount to see how it would look, I appreciate the link very much, I hadn't found any scope mounts that fit my barrel size until now, thank-you Would you suggest just getting say a shock pump with the chamber volume I currently have? The air compressor that I use only pumps to around 45PSI as its very old... Is there another photo of that bolt mechanism? I just can't see if the outside plastic piece is attached at the back or not. Thanks again,

Keringkien

[wyz2285]

you could just glue a rail on the gun for the scope I used fiberglass.

[jackssmirkingrevenge]

jack I tried that bolt action! It doesn´t work !! once a miss load it stops reload completely all the air just come out from the front.

You mean as a semi-automatic? I tried it too at 100 psi and there was too much friction. With HPA or a manual reload it should work just fine though.

When the piston was a little tighter (It's just a screw with tape around it at the moment) I could fire it with the schrader valve, which surprised me because it was a really simply made piston...

I'm surprised it works at all. Your heart is in the right place but you need to optimise your materials if you want real performance

Would you suggest just getting say a shock pump with the chamber volume I currently have?

You will die of old age before you get it to 200 psi with a shock pump - besides, it will tear your current piston apart!

Is there another photo of that bolt mechanism? I just can't see if the outside plastic piece is attached at the back or not

The plastic is just a mould which was later filled with marine epoxy.

Have a look atthis project. I think it's close to what you want to achieve and can be made without sophisticated tools or unobtainable materials.

[POLAND_SPUD]

You will die of old age before you get it to 200 psi with a shock pump - besides, it will tear your current piston apart!

what he wanted to say was -> get a fridge compressor for god sake (ohh and reduce chamebr volume)
LINK>>
http://www.spudfiles.com/forums/my-comp ... 11866.html

[Keringkien]

You mean as a semi-automatic? I tried it too at 100 psi and there was too much friction. With HPA or a manual reload it should work just fine though.

Hmm I'm still not quite understanding the components of that mechanism...

I'm surprised it works at all. Your heart is in the right place but you need to optimise your materials if you want real performance

Yes I too was surprised, I had another piston made out of duct tape and a bolt, it didn't open it every time so I made this design and it works with the schrader valve. I'm thinking a major re-design to mimic the oak stock link you sent me, I am presuming that his was a barrel sealing piston with a slit cut down one side? I like that his is so compact, Australian hardware stores are terrible :/

You will die of old age before you get it to 200 psi with a shock pump - besides, it will tear your current piston apart!

Haha I was thinking of making a portable storage device to hold my air while I'm away from my compressor (I will have to get a fridge one!). Will it tear my piston apart if I have a rubber gasket on the front? I was thinking maybe the back slam of the piston might damage it but not so much the pressure of it against the barrel? Thanks again for the fast reply's!

Keringkien

[jackssmirkingrevenge]

Hmm I'm still not quite understanding the components of that mechanism...

Here's the sequence:

[Keringkien]

Hmm I'm still not quite understanding the components of that mechanism...

Here's the sequence:

Ahh I understand completely now Thankyou very much for your help... Unfortunately I will have to implement this design in another gun, I've started putting epoxy on this current one :/ It's going to look like VH_man's "stick guns", muzzle-loading is the only way to do mine currently. But hey! that's ok, More time in the workshop I will post some pics soon of its current shape soon....