ramses wrote:How are you keeping the mag from just dumping it? I don't see any lips on the mag, or a "top" on that breech.
Does this picture
of the current setup answer your question?
I've done extensive testing and it doesn't seem it's going to work as is - in order for it to work, the o-ring seals in the breech are unavoidable, and they entail a certain amount of friction which the bolt has to overcome in order to chamber the next round properly. If I make the bolt strong enough to do this however, the cartridge then doesn't have enough energy to overcome the bolt stength and eject itself.
POLAND_SPUD wrote:Oh before anyone asks I mean the mechanical valve that cuts off air supply as soon as the bolt retracts, not the air cylinder
That would help with air efficiency but not with the function of the bolt, the fact that air supply is continuous is not the reason that it doesn't rechamber, it's mostly the friction as stated above.
Potential solutions include:
- increasing cartridge diameter, this will not only increase "chamber volume" but also provide a greater surface for the air pressure to push on and eject the cartridge. I'm toying with the idea of using spent 7.62mm brass for this, my only gripe is cartridge shape consistency when it comes to sealing the in breech.
- increasing pop-off pressure from the current approximate 200 psi, this would entail a certain amount of fiddling with materials though and is a sweet spot of pop-off pressure that is not easy to achieve without adjustable seals in threaded fittings.
- accepting that rechambering a fresh cartridge is not really a design requirement, and I would probably be happy to fire one shot and watch the cartridge eject, then manually push the bolt forward to load a new cartridge for the next shot. This would make full auto impossible (unless you use some externally powered bolt like our Polish comrade suggested, but as he correctly predicted this is beyond the complexity level I'm willing to tolerate )
but there are BBMGs for that
A bit more musing is in order, also following my recent experiences with a larger bore hybrid
I'm thinking of marrying something the size of my combustion cartridge experimentation
with low mix burst disk cartridges and make a big f***-off XM109
So many projects, so little time!