SpudFiles

Ok, I have been working on building a gun that is completely portable, in other words, I don't have to hook it up to a compressor or to a seperate air pump. I have tried my hand at building a single action air rifle, a spring piston air rifle, and a pcp air rifle. I have failed at all three. I got the farthest on the pcp gun, I had the hammer valve functional, but it was leaking badly, so i scrapped it. I was wondering what your Ideas were on building a portable gun. I don't really want to use co2, but I want to hear your ideas. Are there any kinds of portable guns I have missed? Do any of you know of any tutorials on building any of these types of guns EASILY? Thanks.
EDIT: Oh, I forgot, this gun would be a .177" (4.5mm) bore gun.

What's completely portable?

I mean I call mine completely portable because it and a full size track pump plus a ton of projectiles can fit into a sizeable rucksack to be carted anywhere.

If we're talking an epic number of shots from a single charge and without using co2+ pressure you're not going to be a happy bunny.

You could get half a dozen shots from high track pump pressure without much problem using partial pilot venting on a QEV. BTB has a working one that uses a hammer valve to pop the pilot side and I've left a trail of random posts over a couple of years and in fact a thread somewhere on how my current cannon does the same thing but using manual valves.

Is that what you're after?



Edit: because you edited: if this is just a 4.5mm design you really do need to get a hammer valve. QEV multishot methods are very inefficient for firing a tiny pellet at a time.

I've been thinking of an idea to take apart a co2 airfost gun and incorporating its mechanism of firing into a homemade gun... It would be powered by co2 cartridges that would gimmie a good hundred shots or so.... I mean you could doodle with it some and see what you come up with

I dunno that's what I would call portable.. beacause you can take it anywhere.. you would just need a co2 catridge ... I'm trying to think up of a way to let a precise measure of compressed air out for each shot with some type of valve.. but i dunno

Boom

Well, As I said I don't really want to use co2. What i mean by portable is that I can carry just the gun and ammo around w/o any kind of external pump...I was thinking of having a multi-stroke on-board pump, I would be happy if I could get a 4.5mm bb to got 500 fps with 3-4 pumps. What I really need is a tutorial on how to make one of these from scratch. Anyone? Thanks for the Ideas.

gippeto has a how to

Well an on-board multi-pump should be obvious..

And no, no-one will spoonfeed you. Have a look through the showcase, mitch made a multipump gun.

As for multiple shots, you won't get them without doing the hard yards.

if you want portable, look into my BOSS system. I dunno how common-place it is on spudguns, but on paintball guns it's the norm.

http://www.spudfiles.com/forums/viewtop ... tml#250427

A multi-stroke onboard pump would work, but for very small volumes, if you're planning on about the same number of strokes at a conventional pellet multi-stroke.

In a pellet gun, the pump uses mechanical advantage and multiple pump strokes to get VERY high pressures in a small hammer-valve-check-valve combination bolted into the pump tube. It is a very small volume of air, but at very high pressures.

If you could achieve the same thing, why build a .177 caliber BB gun? Kind of boring when you can walk to the store and get one for about 20 bucks. I would work on the same thing, just with a few more pump strokes and a larger bore not common in conventional airguns, like 3/8" or 1/2" or even 3/4" ID. Would take a much longer pump stroke and more strokes... maybe a wider pump bore, but the shot's power would more than make up for it.

As far as the valve goes, a hammer valve is just about the de facto standard. The pump bore (and air reservoir) is usually stacked under the barrel, with a perpendicular port to the hammer valve which dumps into the barrel, usually behind the pellet and around the bolt. Take a look at the bottom of this page for an example of a PCP airgun (uses just about the same operation principles, just a different power source) made during WWII. Been around for a bit.

If you're going single shot in large bores then hammer valves get less practical. A QEV would be a better idea (spring so it could be filled from chamber). If you want to stay with a hammer valve, but have to face no opening pressure i can find my pictures i drew up for a co-axial hammer valve air cane.