So, very shortly after the HAMP was posted,
I discovered that putting a hopper on them created a ridiculous assault weapon. Hoppers were easy to make, and a good HH could be made by applying the lessons of the tagger blasters.
So, I didn't think that I needed a writeup for how to make a sweet hoppered HAMP.
Having seen a variety of hoppered-hamps created by the community, I decided that a writeup was necessary to protect the reputation of the HH, which many now see as synonymous with the HAMP. Also, I have refined the make of the HAMP itself a bit, and that's worth an update.
The biggest timesaver and durability enhancement by far is the replacement of the cardboard/duct tape capping of the plunger head. If you chamfer the inside edge of the plunger, and the outside rim of the cap, you can hammer a 1" endcap into 1.5" PVC. Flat endcaps are much better for this, because you can set the cap on the ground, and hammer the tube onto the cap. RagrizInferno is responsible for showing me that trick, among others.
The flat endcap also allows you to easily integrate a check valve into the plunger head. This helps prevent sucking darts backwards from the wye, which can cause all kinds of bad things. This basically requires a hole and a flap. I did it with a piece of rubber sheet, and two small wood screws, as shown. This isn't the best or the only way to do a flap, but it works.
The alternative plumbing for an external check valve is generally uncomfortable or otherwise in the way. Note that not every HAMP should get a check valve--Singled blasters that muzzle vacuum load need to use that suction, as do blasters like the autoloading tagger blaster that otherwise use the suction from the draw.
The next step is to make the air do a 180. Although it's possible to make a hamp entirely inline, it's an ergonomic disaster. Besides, the barrel comes in handy for a plunger guide later. First, cap the end. I don't care how you do it, but the easiest way is to just glue in an 2" endcap. Next, drill the neatest 5/8" hole that you can in the side of the endcap, as far towards the back as possible. Then cut a 3" + (size isnt important yet, you're going to cut it down later) piece of CPVC, and cut off one side of it as shown. This allows you to bottom out the CPVC in the plunger tube, and still get airflow. Next ream some PVC to 5/8", and sheath in around the CPVC. Then, stick it in to size it, and cut off the excess. Pop on an elbow, and use hot-glue / e-tape / bubble gum / epoxy / whatever to seal it. Note that it doesnt need to be particularly strong, as it will be structurally reinforced later, and perfect seal isn't crucial with HAMPs.
Edited by KaneTheMediocre, 13 August 2010 - 09:15 PM.