RSCB Guide

I didn't invent these.  Credit is generally assigned to a few parties, but as best I can tell I think 3DBBQ made them first.  If any one can point to the websites or forum threads that show it's origins more clearly let me know.

The RSCB is an extremely versatile and simple feed mechanism that can be built entirely out of PVC, standard PVC fittings, and a barrel.  It can work with a very wide variety of ammunition, and requires only parts that can usually be found at a local hardware store.  Once the darts are loaded into the magazine, darts are individually loaded by tilting the blaster down so that the next dart falls and sticks into the barrel entrance.

Assembled, but not attached to a blaster, they look something like this:

Shown below is a short barreled RSCB in pieces.

The barrel should be some tube that has at least a slightly tight fit for your darts, and the entrance should be chamfered so that darts can easily fall into the barrel and get stuck.  Shown here is a 1/2" CPVC pipe, with orange duct tape on the tip and a short piece of 1/2" PVC pipe is used to fit the barrel on the 1/2" PVC Tee

This is what a nicely chamfered CPVC / PVC barrel looks like.  Your methods may vary with your materials, but the basic shape should be the same.  Ryan talks more about doing this in his Guide to the Standard Wye Hopper.

The Tee just needs connect the magazine, the barrel, and the air source.  Shown is a 1/2" PVC Tee, but other similar pipe fittings will work if they mate to your other materials.  1/2" CPVC Tees are a smaller, choice that reduces deadspace and makes a 5/8" OD barrel (like CPVC) easier to attach, but won't fit a clear 1/2" PVC pipe for the magazine.

The magazine needs to have a very loose fit for your darts, and it's also strongly recommended to be something clear so you can see how many darts you have left.  Shown here is 1/2" clear PVC pipe, which is more expensive than opaque PVC and usually needs to be ordered online.  Clever and stingy nerfers have gotten around this by drilling holes in an opaque magazine tube, then wrapping clear tape over the holes.  If you're using a CPVC T, then the only hardware store option is usually a thin walled brass tube with a 5/8" OD, but that's not clear and won't take well to the aforementioned hole and tape trick.  McMaster sells 5/8" OD x 9/16" ID nylon tubes (link)  that are translucent enough to see the darts, as far as I know that's the best option that size.

The Cap just needs to seal the back of the magazine.  In a pinch, duct tape would work.  However, in order to avoid partially disassembling the RSCB every time it's loaded, many people put a ball valve on the back of their magazine.  This allows the magazine to be opened to allow darts to be inserted, then closed to make the RSCB airtight again and ready to fire.  Some have gone further and created "dart doors" that allow darts to be inserted and automatically seal behind them--unfortunately, making robust and reliable dart doors is difficult.

The Elbow and Stubs are just plumbing to get the air to the barrel and to hold the RSCB with the barrel pointing forward.  The shown configuration is for mounting to blasters with a front air output, and in this case uses 1/2" PVC pipe segments and a 1/2" PVC elbow. Usually it's easiest to mount the RSCB above the blaster, but below or to the side is actually preferable for smooth feeding, as the dart doesn't need to slide over the air source hole as much in those cases.

Once you've figured out what parts you're going to use, just put them all together and attach to a blaster with decent air volume output.  RSCBs usually require less air than a hopper, so they are often used with modified blasters and small homemade blasters.   

Double-fires are common with RSCBs, and are caused by the first dart falling so far into the barrel that the tip of the next dart goes in as well.  A tighter barrel (or at least barrel entrance) will usually reduce this problem.  If the blaster is tilted up after being loaded, sometimes the dart falls out of the barrel back into the magazine, resulting in a non-fire.  This often caused too tight a barrel or not having a deep enough chamfer on the barrel entrance so the dart can't stick as well.  This is a more nuanced problem that won't go away unless you get the barrel entrance fit just right so the dart stick and stays in the barrel entrance.