Fantasy Firearms is a 10-page PDF for 3.5 OGL Roleplaying written by Eric Karnes and published by Scorched Urf Studios. It brings firearms, of a fantasy nature, to the (gaming) table.
If you want to mix firearms with fireballs and pit musketeers against mages, this could be a useful supplement for you. Interesting ideas for those who do not mind pistols with their magic swords and wands but the supplement is very general in scope and may not provide enough information to allow firearms to be easily introduced or integrated into a campaign.
This book talks about firearms and the way the various standard fantasy races view them, dwarves discovered black powder, gnomes are fascinated by firearms and so on. Though, oddly, the first race to use firearms is not discussed.
While pistols, muskets and cannon, along with exotic melee weapons that use gunpowder are statted out, the actual technology of firearms is not discussed. The means used to ignite the gunpowder is simply absent, no discussion of the differences between fire locks, wheel locks and flint locks. Just as the problems of making or transporting black power in a world filled with magical as well as just physical way to cause it to ignite and thus explode. The firearms and ammunition are entirely self contained and available ‘off the shelf’ with no attempt to place them into a large context, they are just one more item you can buy anywhere.
Four new feats involving firearms or ranger’s fighting styles are included along with three new spells affecting firearms. One new magic weapon enhancement (usable only by firearms) and seven types of specific magic firearms and ammunition are provided. Some of the magic ammunition is clever but nothing here really stands out.
The simplicity of the firearm system presented in this document is good for ease of play but it also takes away from the uniqueness and interest of firearms. Further, there are no suggestions or ideas for how to introduce or incorporate firearms into an existing campaign. Useful as reference but it could have been so much more useful with a bit more context, but real world and how to apply it to a fantasy one.