I've done a fair amout of research on this subject, but come up with no more than you. I have an idea for a larger, (450-500+ rounds) that would come prepacked is disposable refill packs. No thumbing hundreds of rounds into a drum mag! The hard part about handling large capacity mags (drum or box) is trying to push rimmed rounds. They don't stay straight. The other option is to pull the rounds with some sort of belt. Usually, that involves a mechanism that is built into the receiver. My goal ( and proposed solution) would allow you to adapt a "pull-type" drum mag to fit common receivers (like a 10-22) without modification and with disposable, pre-loaded refill packs.
I'm too slow a typist to explain it here, although I think I did a year ago or so. Look here:
http://thehighroad.org/showthread.php?t=101885&highlight=disposable+drum+mag
Actually, in order for the disposable part to be cheap enough, it would have to be inserted into a metal (or hard plastic) outer shell that included the mechanism to fit a particular firearm and the drive spring. The thin plastic disposable pack would fit inside and, hopefully, be universal for all outer adapters. It would also have a thin disposable tape that acts as the belt. The tape would have holes (like old fashioned rolled caps) that would be driven by a tractor gear (like old tractor-fed printers). The tape would have cross-wise ribs on one side that are the thiskness of two rims (so the rounds stay parallel). The rounds would stay in the notch by being pressed against the outer wall of the disposable pack (think thin plastic like a milk jug). A flat steel band would be rolled up in the middle and would unwind (expand in diameter) as the rounds are pulled out and used up from the outside in.
For a 10/22, for example, most of the rounds would be "pulled" while the leading 5-6 rounds are "pushed" by those behind and fed in the same manner as a regular 10/22 mag.
Because of the weight (and size), I think that the only ones really interested would be those who have one of those 2 barrel 10/22 crank action "gatling" guns or the like. A 500 rnd drum would be at least 8" in diameter. The only way it would be economical enough would be for a major ammo company to add it to their product line.
It's a fun idea, but I doubt there is sufficient market to make it cost-effective to manufacture.
There. I explained it. It's in the public domain. have at it.
