Building a pneumatic multi shot rifle.

nathan9117 · Thu Sep 05, 2013 6:14 am

Okay so here is my first proper post on actually making something. I will upload pictures in a couple of hours but I have been awake all night again so I need to sleep for a couple hours. Anyway sleep aside I will explain what I want and the reason for posting here is because Spud files well its full of home made air gun nuts and I figured where better to get help and advice from other than the #1 homemade air gun or air cannons etc.
I currently have a small car sized fire extinguisher with a shrader valve fitted to the back of it for filling. I removed the handle as I wanted to access the nipple of the valve stem for the hammer type valve. In general you could say my mechanism for multiple shots is done well the air side of things where shooting projectiles is concerned. But and here is the main problem I am having. I need someone to help me on how I would build a very simple trigger mechanism that has a bolt and trigger so that each time I cock the bolt and shoot it strikes the hammer valve on the fire extinguisher causing the round to be fired such as a pellet or small BB. The main problem I am having is building a trigger mechanism and bolt with minimal tools and minimal bits and bobs. I currently dont have any sheet metal that I could use as the housing for a trigger but I do have some 9mm plywood that could be cut and used as a housing. So if anyone has any suggestions on a simple hammer and trigger mechanism that could be used to strike the hammer valve to release a burst of air I will be in business. I must mention I dont want the hammer valve to be held open and let all the air out ! I want to be able to use multiple shots from one fill.
Also as soon as I get some money in my pocket I will consider buying a 2/3 valve a 2 way 3 port valve then my trigger would be sorted. But I want to see what can be done with minimal tools and resources to make a setup for my hammer valve. Cheers.
Also I do have some pewter ! so if needed for a trigger and sear I could mock up a wooden template and pour some pewter into it for a trigger and sear. Its just the bolt that is the hard part for me having never made a multi shot rifle before.
Thanks all help and suggestions welcome because I need help on this big time. Cheers.

Gun Freak · Thu Sep 05, 2013 8:31 am

LnL showed me how a spring loaded dead bolt for a door can be used as a pre-made store-bought hammer. You have a Home Depot nearby?

nathan9117 · Thu Sep 05, 2013 7:15 pm

Gun Freak wrote:LnL showed me how a spring loaded dead bolt for a door can be used as a pre-made store-bought hammer. You have a Home Depot nearby?

Dang no

no home depot sorry I live in the uk :O but if you could possibly send me a home depot link I could either order one or look for something similar on ebay ? cheers.

Gun Freak · Thu Sep 05, 2013 8:59 pm

Any hardware store around you might have one.

The actual hammer part of a hammer valve is always the hardest part. Everybody does it differently. I suggest you just look at all the hammer valves in the showcase and base your idea off those examples. It seems hard at first but when you realize how they work you can make one with a little bit of time and effort, physically and mentally!

One thing that I may note is that fire extinguishers are notoriously hard to depress so you will need a pretty beefy hammer. For example, a large bolt with a strong spring behind it, housed in metal or plastic pipe with a retention cap to keep the spring inside. For a sear, drill/file/dremel a slot in the bottom and figure out a simple lever device to extend into the housing and hold the piston back. For cocking it, screw a bolt into the side of the piston that slides in a channel on the side of the housing, or pull back with a cable attached to the piston that comes out the back.

Just a few things to think about.

nathan9117 · Thu Sep 05, 2013 9:42 pm

Cheers for that. I may replace the spring inside the FE hammer valve so that I can use a less beefy spring etc. I have some lengths of 15mm copper pipe so could use that to house a spring and bolt but I need a way of attaching it to the fire extinguisher valve top. Also do you think it will work decently for multiple shots ? say 120 psi in the bottle or I could use some fittings and use an old paintball tank with more pressure in ? cheers.

Gun Freak · Thu Sep 05, 2013 9:52 pm

I'm a master of attaching thing when there seems to be no way. Post some pics and I can help you out.

It's hard to say if you'll get a lot of shots... But generally fire extinguishers are much larger than the typical hammer valve chamber. With that said, you'll probably get a decent shot count. But this depends on your valve dwell time which is dependent on how strong your hammer and valve spring are and how heavy your hammer is... Which is all controlled by what caliber your barrel will be and what your main ammo will be.

Provide us those details and some pics and we can help you out much more

nathan9117 · Thu Sep 05, 2013 10:13 pm

Righty ho The barrel will be 6mm for either airsoft BB's or metal ones

. and here is a picture of the fire extinguisher hammer valve.

And this one is the air outlet port where it will connect to the barrel etc.

I just need a way to connect this to a pipe so I can put a spring and bolt in the pipe

cheers.

Gun Freak · Thu Sep 05, 2013 10:38 pm

Is it an aluminum tank? What does the label say about pressure testing and what it is normally pressurized to? How big is it?

For mounting the hammer pipe, shouldn't be that hard. That little hole (looks like where the trigger level used to be) can be used to your advantage. A bracket can be fashioned for your hammer tube that can be secured with a bolt through that hole. It also looks like there is a little knob on the other side of the valve stem that you can use for securing the tube from the other side.

nathan9117 · Thu Sep 05, 2013 10:49 pm

I think it is aluminium yes and it had no label sorry

it was bought by my uncle like 7 years ago so the label was long tore off but the little gauge on the side of it says 400 psi or 28.12 bar. The size of it is 20 cm tall and about 8cm wide. And yeah I did try it before but the placement of the pipe for the bolt and spring is off from the hole so I would have to fashion a bracket either side and weld or solder or even epoxy it to the tube containing the bolt and spring. As it is 4.45 am here I cant go outside and start bashing at pieces of pipe to make something but as soon as it turns 8am Im off outside to get crafting haha. If I can find it I have a flat chassis made from aluminium for a 1/10th scale rc car I might be able to cut some pieces out of that for brackets.

nathan9117 · Fri Sep 06, 2013 5:01 am

Quickie, Just found a perfect sized spring for 15mm copper pipe. Its a spring from my old bb pistol 7.5cm long and 13mm Dia fits perfectly inside my pipe. Now any ideas what I can construct a bolt from ?

nathan9117 · Fri Sep 06, 2013 5:38 am

nathan9117 wrote:Quickie, Just found a perfect sized spring for 15mm copper pipe. Its a spring from my old bb pistol 7.5cm long and 13mm Dia fits perfectly inside my pipe. Now any ideas what I can construct a bolt from ?

Also just found 6cm by 7cm at 2mm thick of aluminium sheet so I could use this for either a bracket or a trigger mech housing.

nathan9117 · Sun Sep 08, 2013 2:34 pm

Sorry for no posts lately been a bit busy working and as people know work means money but no time. No work means no money but plenty of time. So now I have acquired some cash I am going to browse the EBAY and see what I can find. I have a question though what would be better ?. Should I either A: Buy a 3 port 2 way directional flow control valve like this one http://www.ebay.co.uk/itm/190837161519? ... 1436.l2649
and use that to make a semi automatic airgun design or
B: buy a Quick Exhaust Valve and a Hand Slide Valve wich will go together to make the same as what is in this video here.
Cheers please reply to me asap so I can get my pieces ordered because it takes 2 weeks to deliver them so I want them asap.

Gun Freak · Sun Sep 08, 2013 8:45 pm

You will get more power with the QEV. You can pilot it with the valve you first linked to also. BTW that is a 3 way/3 port/2 position valve. Not 2 way.

What's this have to do with your hammer valve?

nathan9117 · Mon Sep 09, 2013 2:58 pm

Gun Freak wrote:You will get more power with the QEV. You can pilot it with the valve you first linked to also. BTW that is a 3 way/3 port/2 position valve. Not 2 way.

What's this have to do with your hammer valve?

Ahh nice one thanks I might just get the QEV and Slide valve and use them in replacement of the hammer valve setup as it is easier to use those 2 pieces than me try cutting out slots in pipe as I have no grinder at the moment nor many other tools. All my tools are at my grandparents but they moved to the country so it takes 1.5 hours to get there. Cheers.

nathan9117 · Sat Sep 14, 2013 10:32 am

Okay so I just got a hand pump for now to test things out while I wait for my fridge compressor to be welded or soldered to a better output pipe. I filled the small fire extinguisher tank to 4 bar and used an adjustable wrench to hit the hammer valve I can get about 10 decent shots out of it. This gave me some ideas as to improvements for the overall design. I want to replace the fire extinguisher tank with either a pcp rifle air chamber or something stronger like a paintball tanks as I really dont want to risk blowing the tank when pumping it to 10 bar or something. The next part ideally would be to put a regulator between the air tank and the hammer valve so that each shot will be equal and I wont end up with 2 100 psi shots then 1 crappy 40 psi shot thats only an example but you get the idea. Cheers I will work on the hammer today.