Finally! A Homemade Slammable Medicine Ball!

Quick background: I tried twice to make a slammable medicine ball but neither held up. Then I found this approach by Pierre Auge on the Crossfit forums. I resolved to give it a try, but didn't get around to it until recently. In the meantime, a new four-page thread based on enhanced instructions from Pierre appeared, and I finally gave it a go. And it worked! I now have a twenty pound basketball that I can inflate so it bounces slightly, and I can slam the heck out of it with no (so far) big sandy mess to clean up. Here's my version of Pierre's instructions (the instructions are his, the particular experience is mine):

1. Get a cheap rubber basketball, the tougher the better. I think I paid $6.
2. VERY IMPORTANT! If you're going to want to inflate the ball, then the very first thing you should do is inflate it and let it sit around for a day or two to make sure the damn thing doesn't leak. I am speaking from bitter experience: it is quite a letdown to spend hours (really, hours!) filling the ball with sand only to discover a leak near the valve (that you couldn't possibly have caused) days later. *&$#! cheap-ass Walmart ball...
3. Once you're sure you have a good ball, grab the spike from a radial tire plug kit (it should include a spike/rasp, a plug-insertion tool, some cement, and some plugs which are basically long gooey strips of rubber or something) and puncture the ball with it. I actually drilled a hole in my ball, but I read later that stabbing might be better, as no material is actually removed from the ball with a stab. So far no problems with the drilled hole though. No matter what, you want this hole to be as small as possible while still admitting the rasp.
4. Insert an inflation pin into the ball valve. This will allow airflow out of the ball when you pour the sand in. Surprisingly important. Oh, so I guess this means you'll want your hole somewhat near the valve so it stays clear of sand as you're filling. I put mine on the next black line over from the value (in the picture above, you can see the inflation pin in the valve, and my hole is very close to the right edge of the picture).
5. Get a funnel. It will have to be fine enough that you can jam it into the hole, but not so fine that the sand won't flow through it. I used one of those diner ketchup bottles (pictured above) with the tip cut off at an angle (I tried cutting the tip square on one, but then I couldn't jam it into the hole).
6. Pour your sand through the funnel into the ball. A surprising amount can be said about the choice of sand. I used play sand and it was a pain to get into the ball. I would fill my ketchup bottle (which also had a hole in the bottom for airflow purposes) jam it into the ball, and a trickle of sand would flow in before it would jam. So I'd jiggle it around, and it would flow a bit before jamming again. So I held my random orbit sander against the bottle, and the vibrations kept the sand flowing. I don't know how long it took me in total, but I do know that I watched all of The Memory of a Killer (good movie!) on my tiny 7" portable player under flimsy headphones against the whir of my orbital sander, standing on the cement floor of my cold workshop and probably only did three-quarters of the job in that time. It would be much better to rig up some self-filling solution, kinda like my ketchup bottle but much bigger so you can fill it and walk away while the ball fills. I'll leave that as an exercise for the reader. Anyway, back to the sand: some Crossfitters recommended silica sand, as it is finer (I think it's used for sandblasting, among other things). I already had the play sand though, and I could only get the silica sand in 100 pound bags. Besides, silicosis is such an ugly word. Very recently somebody suggested using sugar, which I bet would flow nicely. You could probably get 20 lbs. for $10 or less. Anyway...
7. After the ball is as full as you want it, rasp around in the hole to clean it, then follow the instructions on your tire plug kit to patch the hole. Then slather the plug and surrounding area with Shoe Goo for a good seal. Leave it alone for 24 hours.
8. Inflate as desired, and get slamming!

A couple other notes:

• Clearly getting the sand in is the big chore. I read on one of the Crossfit threads folks that recommend an approach where you slit the ball or cut a flap into it instead. When I did this the ball did not hold up to slams, but it's entirely possible they are better patchers than I am.
• Suddenly $50 or whatever it is for a twenty pound slammable ball doesn't look so bad. :-)
• Thank you, Pierre, for the great instructions!