SpudFiles

Testing an idea I had for a semiauto tube fed gravity feed and it seems to work, air goes up into the magazine and pushes the balls back up the tube because of a small amount of air bleeding out of the top of the tube, when the pressure builds up enough the front ball pops out like a cork as there is a narrow piece at the start of the barrel, (3/4" copper)

This system worked perfectly for me, which is what makes 25 bb's of lead rise, caliber .22 in my replica of MAC 11. viewtopic.php?f=29&t=26856I used a small flow regulator to regulate the amount of air that rises through the tube that it keeps ammunition.
What I don't like is that it wastes air, but it's an old idea that it works. Check out my video of the MAC 11.

hectmarr wrote: ↑

Sat Apr 17, 2021 3:23 pm

This system worked perfectly for me, which is what makes 25 bb's of lead rise, caliber .22 in my replica of MAC 11. viewtopic.php?f=29&t=26856I used a small flow regulator to regulate the amount of air that rises through the tube that it keeps ammunition.
What I don't like is that it wastes air, but it's an old idea that it works. Check out my video of the MAC 11.

Yes I remember that, it was amazing

With some paint

Nice work. I like it for its simplicity. I assume that the tube that houses the large balls is plugged at the free end?
What pressure do you use to shoot? I would like to build one to launch projectiles in the shape of grenades, but with the same shape ...

There is a loading gate which is not a tight fit so it lets out enough air to keep the balls pushed up, it fires really good at 100psi.

ok I understand. I plan to use around that pressure that you use, 7 or 8 bar, because much more is more complicated for me. In the future I will build it. Good idea of yours to arrange the tube that houses the balls at an angle, because it is comfortable and aesthetically good. Placing it at 90º with the firing barrel would be an aesthetic aberration and much more uncomfortable. As seen in the photos he is beautiful, and compact.

Bit of a cosmetic update, just need to get a spring on the loading gate, makes a mess if I forget to close it

Very nicely done! I really like the magazine lid.

A practical implementation of the valveless/popoff concept.

jackssmirkingrevenge wrote: ↑

Sun May 02, 2021 7:28 am

Very nicely done! I really like the magazine lid.

A practical implementation of the valveless/popoff concept.

I could never solve the issue of the retention of a "cup" type pellet, to shoot the same as your animation, but with a hybrid.
The problem is that I cannot insert the retention o'ring, or any other type, into the rifled barrel. The pellet does not go straight if you leave it outside the rifling, when you shoot, it has to be inside.
The system works perfectly with a simple o'ring, (compressed by a screw to regulate the retention), for spherical steel ammunition, I am shooting with some weapons like that, and it works perfect.
I think that the lead is very soft to maintain the circular shape of the skirt of the pellet when passing through the retention o'ring, although the shoulder of the pellet can hold, I do not know, but it is very good to design something simple and effective because we could shoot with air or a hybrid common pellets, without the need for a trigger valve or rupture disc.
My last tests with my "captive ball valve", which is basically the same adapted to a hybrid that shoots bb's, and a hard o'ring, extracted from a CO2 canister, retains a 1/4 bb of zero. "up to 60 bar without letting it go ... I didn't expect it to work but it works fine.
Unfortunately, the retention of the pellet only, when it is stuck in the grooves, is little, and in the case of hybrids it escapes at little pressure, and little of the energy generated is used.
To safely retain the compressed air-gas mixture, it is necessary an elastomer of unknown location and shape on these sides, and of variable resistance.

I've had this issue with o-ring detents and pellets, the head pops through but then the tail gets stuck on the o-ring.

That's the good thing about the soft foam balls, they deform then reform.