I'm an S.M. Sterling fan as well, one of those O'Dwyer VLEs, among other fun gun related commentary, appears in his latest.
John D. MacDonald is also great, although there's one where Travis McGee vents some anti-handgun feelings.
Being into wierd stuff, I'd also have to nominate E.E. Knight's Vampire Earth books; in the latest (second) book the hero packs a PPD-40, and there are interesting ideas about how alien cultures would approach smallarms design. Mostly he dosen't get so specific, but it's pretty great action/sci-fi adventure.
The whole Executioner series, and anything else in the Gold Eagle imprint, (Able Team, Pheonix Force, Deathlands, etc, etc...) are pretty lousy, but are decent airplane time killers. Gold Eagle turns them out like Nike makes sneakers. Jerry Ahern was better, IMHO, because in the gun magazine columns he used to write you could see pictures of him shooting a Detonics .45 in each hand... research?
Freehold, which I want to say is by Michael Williamson, is another one that's popped up on the boards which I enjoyed very much.
Koontz has mostly good reads, although Phantoms tried my patience.