http://fbcdn-sphotos-a-a.akamaihd.ne...08146982_n.jpg

Earlier this month I made myself a new cylinder for the Giffard. The original cylinder is in good condition and holds CO2 perfectly fine. But for everyday plinking, I figured I would convert the Giffard to HPA.
________________________________________________

My Giffard will shoot the 8mm, 49grain ball at around 600fps producing around 40 Ftib at the muzzle on co2. Perfectly adequate and the co2 fill provides plenty of shots.

For me, filling the co2 reservoir can be a pain, as I use the large co2 tank mainly for craft brewing so need to swap fittings and invert bottle etc. So for ease of use I thought I'd swap to air.


The original cylinder was obviously intended for co2, but you can fill the cylinder with air to around 60 Bar and have enough air for a couple of shots. But thats it, any more air pressure then valve lock sets in and muzzle velocity drops off ...+ the cylinder was not intented for any any more pressure. Since your not going to start modifying your antique rifle fitting a new hammer spring, your out of look with the original cylinder.


So I designed the new cylinder to run on air with a assisted valve, which can be opened at much higher pressures by the relatively weak Giffard hammer / spring. So you leave the Giffard rifle untouched.

The new cylinder is the same diameter as the old one, but longer, stopping just short of the sling mount to give 130cc reservoir volume. Hopefully its aesthetically well in keeping, for the age and grace of the old girl.

With the cylinder fully topped up at 200bar, the rifle can thump out the ball just subsonic at 1030 fps, producing a whopping 115 Ftib.


Turned down a little you can get 15 shots at over 800 fps / 70 ftIB from a single fill. Or turn it down more for more shots.


It’s a real hoot to shoot

Chris

http://fbcdn-sphotos-e-a.akamaihd.ne...93485490_n.jpg