Weight of Bullets for Sling

[scp]

OK, so the Arms & Armor supplement says that a sack of 20 sling bullets weighs .5 lbs I am thinking this is a little light since they are 3 inch long lead bullets. The D20 SRD says that 10 bullets are 5 lbs, which I think is *way* too heavy, especially for something that gets destroyed on impact.

I have even geeked out and looked at modern Daisy Slingshot Steel (zinc coated) Ammo, and 20 of the 1/4in ball-bearing type weigh .3 lbs!

I know I am over-thinking this, but how do you guys deal with them?

EDIT: More geeky-ness: The interwebs says that a piece of steel is 68% of the weight of same sized piece of lead. So, by my sh!tty math skills that means that twenty 3-inch-long lead bullets should weigh closer to 5 lbs, and I am thinking the decimal is a typo. I know I am over-thinking this, but it's stuff like this that floats my boat sometimes.

[serleran]

If the ball is 3" in diameter, it weighs almost 6 lbs. That is for one.

Weight = Volume X Density.

Volume = 4/3(Pi)(Radius^3) = 4/3 * 3.14156... * 1.5^3 = 14.137

Density = 0.409

14.137 * .409 = 5.782 pounds

I'm thinking the bullet is a lead shell... not solid. Or, it is much, much smaller. Because of the exponent, the bigger the ball, the more it will weight. It gets much less the smaller it becomes.

I'd go with 20 bullets weight 10 pounds, each at .5 pounds and around 1.5 inches. That's a rough amount, not a precise one.