gingerbrew, I filled a 330ml bottle today and it worked really well, took about 30 sec to fill the bottle with about an inch of head space left at the top.
the tools I used for this build was:
a battery drill
drill bits 3mm - 8mm
high speed rotary tool, aka a dremel , with a single cut bur
hacksaw
parts used
some scrap stainless steel sheet
aerpro ap122 aerial from super cheap auto
ELBOW M STD COMP BRASS #5 1/4"TX1/4"BSP
VALVE BALL MINI BRS N/P SCD F/F 1/4" 8MM
CONNECTOR M QCK KQ2H08-02SX2 8MMTX1/4BSP
a spring
and a small o-ring
selley's glass silicone sealant
Get the aerial and unscrew it from its base, cut off the bottom of the stainless steel tube so the tubes can be removed from each other, give them a very good clean especially inside of them.
take the two tubes and trim both ends so you end up with 2 straight tubes,make the larger one about 1.5" shorter than the smaller one, the larger one OD is about 7mm and the smaller one about 5mm.
Now to bell out the bottom of the smaller tube, drill a 5mm hole in a piece of timber so that the small tube tightly fits through it, put one end of the tube into the chuck of the drill and gently tighten ensuring that you don't damage the tube. Push the piece of timber over the other end so that about 4mm is protruding from the timber. Start the drill spinning holding the piece of timber still, now with a small stainless steel rod, I used the top part of the aerial, start applying outward pressure on the part of the tube protruding out of the timber, slowly moving the stainless steel rod out, you will soon see the end starting to bell out. Make the bell large enough so that it will block the larger tube.
get the elbow and drill a hole up from the compression side through the top of the elbow slightly larger than the inner tube, get a 7mm drill and bore out the inside of the compression side of the elbow to give more clearance for the gas to go around the inner tube being careful not to go to far.
With a 7mm drill, drill out the compression nut and olive from 1/4" to 7mm, because the olive is made of brass this is a bit tricky.
make up a trigger out of the scrap piece of stainless steel, drilling a 7.5mm hole in the bottom to fit over the outer tube and a 4mm hole in the top that needs to be elongated out to the edge with the bur on the rotary tool so it can be clipped on to the inner tube
the bottom stopper was the most difficult thing to make, I had to shape a stainless steel bolt to the shape I wanted and then stamp it into a stainless steel sheet to make a mould. Then I had to coat the mould in wax so the silicone would release from the mould. I then made the clip that fits around the outer tube, I then put the end of the clip into the mould and put in the silicone and waited for it to set and then trimmed it up.
put a ridge in the bottom of the outer tube to hold the stopper by using a straight edge piece of metal and rolling the tube back and forth under that bit of metal with a bit of force and the ridge will be created
cheers steve