I posted earlier that I was resurrecting an old Excellent Gevaret CII that shoots 5.4mm lead ball.
The rifle is now seemingly quite airtight and the valving working. The inlet valve was repaired with some 1.5mm silicon tubing that fishermen use to put on their floats. Outlet valve was repaired with a disc cut from some rubber sheet. Air leaks in various threads were repaired and a hole in the pump soldered.
During testing I was using 1cm sections of plastic rod (ex kid's paintbrush) and was achieving very low velocity ... I was catching the rod bits in my garden jacket.
The last attempt had the rifle showing healthy resistance to pumping and at 6 pumps the plastic rod shot through two layers of my old jacket and into my backstop box. Success!
But I have no 5.4mm ball. I tried making a sizer to size 5.5mm Wasps down to 5.4mm but it is very difficult to push a 5.5mm pellet through a tapered hole to reduce it to 5.4mm! So I resorted to putting the Wasps in between two steel plates and rolling the pellet to size. Very crude method but it works, producing more of a slug though. These fire very well and I can now believe that the rifle could achieve its claimed 10ft lbs with the 5.4mm ball.
And all this from a bicycle pump mechanism. A guess lets me estimate the air cylinder as about 7cc with the pump pushing, say, 21cc of air in at each pump. So each pump provides about 3 bar. So 10 pumps would give around 30 bar in the reservoir. All air is ejected on firing so you use about 210cc of air. Not bad for an old rifle.
I am still trying to find some 5.4mm ball though....
Cheers, Phil