This is a discussion of a new type of hopper mechanism for use on homemade nerf guns.
When I first became interested in Nerf as a hobby I thought that the tiny breeches inherent in stock nerf guns were the culmination of reloadable design. After a bit of research I found out about brass breeches, which allowed for much longer barrels but still required a mechanism to "cycle" the breech from open to shut and back again. More digging uncovered the speedloader, shotgun attachements and other clever devices for powerful guns that didn't offer much in the way of rate of fire, but capitalised on power per shot, culminating in the RSCB. My cup of tea leant more towards massive dart spamming at medium range, so I was not satisfied.
Finally, I found out about the Wye hopper, capitalising upon both high rate of fire (all that is needed is a prime and a trigger pull, which is much quicker than even RSCBs) and power. Their ability and reliability was enhanced over time, leading to the modern, effective design. You've probably seen at least one b now, but here's a nice picture demonstrating exactly what they do:
Simply put, the blue part is the hopper, or clip/magazine where the darts are stored (you can see 5 in there if you look closely, the purple part is a simple PVC end cap, the red part is a PVC wye and the green part is the barrel. Air is forced into the wye piece through its open side, and the resulting suction on the dart at the top of the clip (whose tip is poking into the main part of the wye) sucks the dart first into the wye and then into the barrel. This leaves you with a fairly reliable mechanism that will fire 1 dart at a time, and is gravity fed.
The problems that occur with wyes (as near as I can tell) are the following:
1. They're super hard to obtain depending on one's location. In Australia (my home country) they're nearly impossible to find, requiring shipping from overseas to obtain them.
2. They can be very unreliable with even slight changes to dart dimensions. This means that using someone else's ammo in a war becomes very risky.
3. The air expended in sucking the dart into the barrel is air that could otherwise be used to shove the dart further downrange, leading to a slight efficiency problem.
Overall, the wye is superior, but with room for improvement.
While roaming the various Nerf fan sites one day I found an interesting take on the wye that seemed to solve all its problems:
This design - which I'll dub the Speed Hopper for want of a better word - dramatically increases fire rate over wyes, eliminates the air inefficiency and improves feed reliability.
The basic idea is that darts are gravity fed one at a time into the PVC T-piece, then expelled through the 45 degree bend and out the barrel via air coming in through the second 45 degree PVC joint.
The basic operation is the same as the wye, with one shot being fired per spring release (if you're using a springer, that is), but has several benefits:
1. Because the darts are already located in a preliminary pert of the barrel, no air is required to force them into the barrel, leading to slightly better efficiency.
2. Because the darts aren't gently sucked around a bend, but instead are fully forced into the barrel, the Speed Hopper is able to cope with different dart lengths a lot better.
3. Air guns can give this thing some serious punch, as you'll see later.
4. The part are so readily available that almost any town in the world with a hardware store should be able to supply them.
The greatest benefit is that the pressure wave from the firing mechanism (be it a plunger or compressed air) does not impede darts sliding into the red PVC T, so larger volume plungers have the benefit of being able to fire two shots at once (by large, I mean bigger than a Maverick plunger). When using good darts, a huge hopper and a blowpipe setup (exactly what is shown above) I can get around 20 darts per second downrange, or 1200 darts per minute. Take that 700 dpm Vulcan!
Overall I am very satisfied with it, as my playstyle is pretty much about intimidation through walls of foam.
I'd encourage you to try it out with a 1meter/yard long hopper and Silicone Darts in the blowpipe setup and see how it goes.