Steel
Version 0.17: This article may not be up to date for the latest stable release of Crawl.
Steel is an ammo brand that causes ammo to deal 30% more damage.
Although lacking in any special abilities, steel ammo is a good choice for general use, but is less effective than silver or elemental ammo when attacking vulnerable enemies. It is a rare find outside of god gifts and certain high-level monsters. It can be found on tomahawks, javelins, sling bullets, and bolts.
Note that while steel is a material in real life, in Crawl, it and silver are implemented as brands, so you can't have a poisoned steel javelin or a silver bolt of flaming.
History
Prior to 0.16, steel ammunition would mulch 10% as often as normal.
Prior to 0.15, steel ammunition weighed 300% as much as normal.