My Disco Double has a .357 cal barrel as one of the configurations.... I can get 3 shots at 170 FPE average with a 127 gr. slug, so an average of 780 fps.... That is with a 3000 psi fill, using three high-tensile (170 Ksi) low-profile valve screws, which Lloyd has tested to shear and we both consider them OK for that MSWP.... I also achieved a bit more power than that using a Cothran valve (200 FPE 1st shot), but of course you get a declining shot string as the pressure drops, whereas my 170 FPE tune was a 4% bell-curve....The Disco reservoir is only 135 cc, and with Lloyd's double tube conversion it comes up to 250 cc.... I don't know of anyone who has gone larger than .357 cal.... You won't get 500 FPE out of a .357 Disco, even for one shot, in fact you would be very hard pushed to get to 300 FPE at 3000 psi, with a 24" barrel.... I have never seen anyone even come close....Bob
If you have a .62 caliber, 36 inch barreled airgun with a 157cc dump reservoir with 3000 psi of pressure, then the average pressure during a shoot would be just under 1500 psi.I think that would be enough for 500 fpe, that would be a interesting build for sure, no idea what kind of valve that could dump so much air tho, not many build high pressure dump airguns.Shooting patched .60 cal round balls around 800+ fps sounds fun for sure! Regrading the max caliber on a 7/8 tube, if a valve that have the whole tube diameter around the poppet head (sealing after the poppet instead of before like in the disco valve housing).It's around 0.75 ID so plenty of area around the poppet for even a .50 cal, the small air volume will be the hold back, although a drop block and a bottle could fix that...Just carry a little bottle in your backpack and fill up between shoots or bring a handpump, 150cc should no be a problem to fill to 3000 psi in the field.One or maybe two shoots are enough for a deer hunting rifle, no need for 3 shoots imo.150 fpe does also sound a little low for deer, I would personally aim a little bit higher but I lack experience in hunting in these power levels so it's maybe just fine?There are always arrows one can load if nothing else, 150 fpe is in the same range as some of the most powerful crossbows out there... Good luck on your hunting!
The Epox Badger is a .40 Based on the QB wich is based on the old crosmans; which is the roots of the Disco also...
There are some work to handpump for sure.So it depends, for mass target shooting with a dump gun and handpump is not practical at this power but for hunting maybe. Some guys get quite amazing group with smoothbores and patched roundballs, could be fun to test some time.Regarding the tube.I would just buy a 4130 7/8 tube, you get pre drilled holes in a disco tube but that should not be a problem to make and you can cut it longer for more volyme.Pin the endcap like the valve and you don't need to thread it. Another idea is to buy one of those cheap 200cc bottles and use them as reservoir, making a threaded valve. 5/8-18 or m18x1.5 is the common threads used.Mount it backwards like an condor or forwards with drop block or raise the breech slightly without a drop block. Could also mount it straight down like the antique big boresThe badger has 1"od tube if I recall correctly? Just throwing ideas out there, love to watch build threads!
a very simple balanced valve thats "overbalanced " but still seats will act as a dump valve every time..you could even have a softer seat too make sure it seals every time as the pressure holding the poppet shut would be very little.
I am not aware of any valves available for the Disco that have an exhaust port larger than about 1/4".... I hardly think that would be suitable for a .62 cal barrel, nor do I know how you could fit a dump valve intended for that caliber inside a Disco tube, which is what the OP desires....A .50 cal barrel that is 36" long contains 116 cc of air.... If you dumped the 135 cc contained in a Disco tube at 3000 psi into that, you would end up with a muzzle pressure of just over 1600 psi, for an average pressure of about 2300 (while the bullet is in the barrel), assuming the porting was big enough (full bore).... If you did everything right, you just might get 500 FPE.... I still don't know how you could build a valve with 1/2" ports and fit it inside a Disco tube, though.... Bob
While you can "fit" a 14mm poppet inside a Disco tube, I have no idea how you could allow enough flow past it, and retain enough wall thickness for the structural integrity of the valve itself....Bob