I'm playing a Chaotic Neutral 7th level rogue/fighter (6/1) in a Ptolus campaign and I need some guidance in selecting a PrC.

Here's some basic info on my character:

Str (12)
Dex (21) *w/temp abilities
Con (14)
Int (17)
Wis (10)
Cha (10)

Primary skills: Open locks (21); Disable Device (13); 10-13 in all other standard rogue skills; craft skills in traps; locksmithing; firearms; alchemy; metalworking; and machines.

Weapons of choice: spyglass rifle; dragon pistol; shortsword; powder bombs

Feats: Lightning Reflexes; Rapid Reload; Precise Shot; Point Blank Shot; Exotic Weapon Proficiency (Firearms)

Obviously the character has a heavy machines and firearms bias, but he's also quite competent engaging in typical rogue activities.

I'm looking for some advice on what possible PrC I could take and/or any interesting direction I could take this character. Is there a PrC specifically around firearms? Explosives? I thought of possible taking the Gnomish Artificer and creating a "Roguish Artificer" but this would replicate skills already represented in the party. I toyed with the idea of moving him more towards an assassin like build, but my DM has a thing about too much nefarious activities being associated with the party.

Any advice would be greatly appreciated. Many thanks in advance.