First, you have to understand that such pieces cannot completely fill the container. They will probably fill it more efficiently if they are neatly packed; the most efficient packing for a large container is if, within each layer, each row is offset half a space against its neighbours:

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For a very large array this gives a "packing fraction" of pi/(2*root 3) which is about 90.6%. That means that for every liter of internal volume you have 906 cm^3 of metal and the rest is air. For small containers optimizing packing near the edges may be more important.

When you write `1" round' do you mean "round and 1" across", "round and 1" in radius" or "round and 1" in circumference?" I'm going to assume the first. 1" is about 2.54 cm so that's a 1.27 cm radius and a volume of pi r² h = 2.53 cm³. Dividing by the packing fraction, each cylinder actually needs about 2.8 cm³ living space.

Now, 3x3x2 ft³ is about 510 000 cm³ [use Google for unit conversions!] which is enough space for about 180 000 cylindrical slugs.

-RD

PS: A rougher but easier estimate: a square packing arrangement

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gives

(3x12) * (3x12) * (2*5*12) ~ 155 000 slugs.

Good Hunting,
RD