Gods of the spud, I call on you experience and understanding

[Bullseye]

Hi all,

I've been lurking for a couple of years now but I've finally found myself in a position to begin experimenting. The main benefit of the time I have spent watching is I have figured out what I am hoping to see from a project.

I'm hoping to build a reasonably hard-hitting 9mm / 3/8" smoothbore gun. My intention is to keep the whole thing beneath 26", probably hosting an air reservoir parallel with the barrel, my intention is to achieve a muzzle power above 200 joules (Although closer to 400 is ideal), by my calculations, using a 9mm lead ball weighing 34.5g I'd need to achieve a minimum muzzle velocity of 353fps.

I'd like to get 4 shots out of the reservoir, and ideally hope to incorporate a bolt/slide action mechanism for loading rather than an open breech or muzzle loading. I would rather a simpler mechanism for firing than complicating it with semi-automatic loading (I'm sure seasoned builders roll their eyes when a new face comes along and says Girandoni, but that's sort of what I have in mind)

I have some experience of metal and woodworking, but I do not have ready access to a lathe at present. I do not have an air compressor, but I have mostly been holding off until I know how powerful a compressor I may need for this job. I anticipate that this will likely need to be made from copper, and i am familiar with compression fittings and also with brazing /soldering (Though I'm not sure how much pressure a shop solder-fitting will withstand, any advice?

From my understanding, I think the most simple ways to facilitate a project like this are either with a QEV (I'd love to buy one, but I don't think any are suitable?) or a hammer valve. The Hammer valve is appealing, but I am unsure of the intricacies of using these at higher pressure?

I had a go with GGDT a while back, but I was unsure of far too many variables to make a reasonable go of it. Would anyone out there who has a better understanding of these things than I do be kind enough to point me in the right direction? Or even better, kindly run some figures through the software for me if they know what they are doing!

I'm hoping that someone will turn around and tell me I'm being silly and that it's super simple to make such a short gun hit so hard, but I'm also ready to be told that the parameters I am talking about aren't really compatible in a use-able gun.

In an ideal world, I would also like to fit a supressor, I note that Jack's Smirking Revenge has done some work with heavy duty versions of these, but I'm concerned about potential loss of power in the projectile.

So, thus my essay is concluded, and I leave myself open to your help, encouragement, criticism and ridicule! Fire away

Thanks,

Bullseye.

[wyz2285]

QEV is suitable and less trouble to make than hammer valve;
Salvage a fridge compressor;
Copper, rather soldered or compression fitting will work fine;
You will not get any power loss with a suppressor, if made and fit properly.
Example of what you want: http://www.spudfiles.com/pneumatic-cann ... 23715.html

[Bullseye]

Thanks Wyz! I saw this gun a while back but never noticed the plans for it! That could be incredibly handy.

am I right in understanding that a hammer, due to it's method of firing, can offer multiple shots from a single chamber?

I don't presently have a paintball bottle, and I'm wondering if the alternative for a fully portable gun would be to have something like a 4oz. CO2 cannister on the fill side of the QEV, although the appeal of the project is having something that can be run from a shock pump if possible.

Each answer I receive leaves me with 3 questions haha. I struggle to comprehend how things work from words and diagrams, I have little difficulty understanding something once i can hold it and take it apart, but until then I'm going to be second guessing myself!

Thanks again,

Bullseye

[Brian the brain]

Yep.Hammervalve can get you multiple shots.
A QEV can be easily modified to be pilotted by a hammervalve wich gives you multiple shots with a lot of added power.

The modification means you can "fill/refill" the QEV from the reservoir-side.
You can use just one reservoir and empty it shot by shot.

This helps to keep the thing compact with a minimum of parts.
It also keeps the pilot volume to a minimum wich makes it act fast and waste very little potential to refilling the pilot volume.

can't get more compact than a CO2 bulb and elbow and the valve internal volume as the entire reservoir I guess:



Worked well although the extreme pressure from the 12 gram CO2 bulb forced me to knock the valve with an actual hammer.
Lots of powerful pops though.

Digging this up makes me want to give it another try someday..

[Bullseye]

Thank you so much for the guidance so far folks, I anticipate that I will operate on a homemade QEV actuated by a hammer valve. I have returned to a post by Wyz which I have watched a dozen times before and I note that with the first type he describes he actually presents us with a hammer valve, however rather than being counterweighted it seems to be weighted against a hammer blow.

Brian am I right in thinking that your hammer valve on the pnushnikov/cases man is weighted the other way? Offering resistance against the vale being closed in order to make it easier to open? I've tried searching (you have a lot of posts!) but can't see your method of doing this in this case.

I'm considering attempting a semi-auto magazine mechanism forward of the QEV, limiting myself to restricted fire with a single action or maybe double action (if I can figure it out!) trigger to strike the hammer.

I'm shopping for parts, am I right in thinking that using a 1/2" QEV for a 9mm (.38) barrel will be the right choice? I feel as though a 3/4 will waste air? Something I'm trying to do by actuating the spring loaded QEV with the hammer valve.

Being in England I am given the glorious choice of several sections in both mm and inches! Lucky me! I'm quite enjoying shoppingfor bits, especially now I'm going to handmade the QEV as it seems to be a struggle to get one rated about 150psi without waiting for it to arrive from HK!

Thanks all,

Bullseye!

EDIT: I have just realised that a counterbalanced Hammervalve negates the need for a QEV, however it seems to be somewhat beyond my current capabilities, especially with my first gun. Doesn't matter how efficiently you use the search engine if you're searching for 'counterweight' instead of 'counterbalance'!!

[Brian the brain]

The valve is placed inside a pressuretube.

Searchterm CBHV..
Counterbalanced hammervalve.

It is not completely balanced though.
Pressure keeps it closed...until you hit the stem.

Using a CBHV to pilot a QEV is overkill.
I suggest using a regular hammervalve on a QEV.