After a couple failed attempts I figured a homemade slammable medicine ball was impossible, but it looks like I was wrong. What you need is somebody that actually knows what they're doing to apply themselves to the problem. Pierre Auge graciously posted his instructions to Crossfit and gave me permission to repost them here:

Actually its pretty simple as long as you're up for some hard work and have some tools.

You'll need the following:

  • A drill with a medium fine bit. (1/8")
  • A funnel with the narrowest nozzel you can find. (to fit in the 1/8 " hole)
  • A rubber/epoxy high pressure tire puncture plug. (Not silicon, it has to be either rubber or epoxy, or rubber with an epoxy resin.)
  • Epoxy resin based high pressure sealent.
  • Sandpaper (or die grinder if you're lazy and want to chance weakening the ball)
  • Radial tire patch (some cordura or old canvas might work too)

Get the toughest Basketball you can get, drill a hole in it. Sit there for about 2 hours pouring sand through this stupid funnel. (Or you can use a machine like I do) Weigh the ball as you fill it.

When the desired weight is achieved use the tire puncture plug to fill the tiny hole. Trim the excess that is sticking out. Use the sealent on the area in and around the plug. Wait until dry and hard. Now put some air in the ball with a pump. Go back to the area directly around the plug and start sanding with your sand paper until the area is quite rough. Take the radial tire patch slather the area with some more resin and put the patch into the resin. Put more resin on top of the patch. This should give you a good seal after it dries for a few hours. (Overnight)

If you are willing to take on this endeavour all the power to you but it took me several attempts to get this to work properly. But on the other hand its worth it because you get a very tough ball.

Hell I've seen an entire company of guys wail away at these things one troup after another and they are going strong.

Thank you Pierre!

With a hole that small I wonder if my Home Depot play sand would even go through (even new in the bag it is slightly damp and clumpy) or if I'd have to buy finer sand from a garden center. Just something to consider if you're going to tackle this yourself.

As for affordable off-the-shelf medicine balls, I bought an 8-pound Danskin ball from Walmart for around $16. It has a smallish diameter (maybe around volleyball-size?), minimal bounce, and a slightly nubby surface. It works great for a variety of slams. You can also get a 10-pound Danskin ball from Amazon for $23 (buy something else at the same time to get over $25 and be eligible for free shipping). Same size and bounciness as the 8# ball, but with a smooth vinyl surface. I haven't had the 10# ball for very long, but the 8# ball has held up well to some good slam sessions, including hitting a rough concrete seam on my basement wall a bunch of times. In addition to slams, balls of this size/weight are good for holding between your feet or knees for weighted pull-ups and dips, and in your outstreched arms for Russian Twists.

UPDATE, 1/9/06: I originally tried the Walmart ball on Ross Enamait's recommendation, but he just pointed out to me that the ball I picked up is not the same as what he found there. Walmart used to carry the Stamina Products 10# ball for $16, but apparently Walmart doesn't carry that product line anymore. As you can see from that link, you can buy them direct for $20, and it might be a nicer ball than the Amazon/Danskin one I have (for the textured surface, if nothing else).