I LOVE the idea for this card, I really do. A big gun-toting guardian tucking a .45 Automatic into their jacket so they can whip out the big guns. There's just one problem and it's pretty clear once the euphoria of taking free potshots at eldritch abominations wears off: How do I fit my brand new .45 into my holster when my hands are already full of Gun? The biggest issue of this card IMO is that it requires you to play your weapons in a particular order. Draw your BAR before your .45 Automatic? Tough luck. Bandolier and it's older brother are almost always going to be better.
Poor Tommy has to throw his beloved Becky away if he doesn't tuck his
sidechick sidearm away first. Lily doesn't know the first thing about firearm safety. Sister Mary is too busy waving around that taboo Winchester she's so fond of. Nathaniel Cho prefers beating his enemies to a pulp in organized events. Mark, Leo, and Zoey might be able to make SOME use of it, but they still face the full hands dilemma.
And that's where I realized the Illicit keyword wasn't just for show. Finn, Tony, Jenny and most likely Bob would absolutely LOVE this card. Between Lockpicks, Flashlights, Magnifying Glasses, Weird Fans, Old Keys and... eyeballs? Flex or combat oriented rogues love to have a gun in one hand and something else in the other.
I feel like this card wants to sucker deckbuilders into making a "moar gun" style guardian which IMO is what Bandolier is for. I feel like this card is less for the Brute with a BAR, and more for the Con with a Colt. I avoided mentioning Roland simply because many people (at least the ones I typically play with) play him as a fight oriented Guardian who just so happens to get clues and so end up running big guns and Bandoliers. Though he'd probably do well with this card running some Magnifying Glasses to bounce for mag swaps if you wanted to go clue focused who just so happens to be able to fight. It's worth noting however that Parallel-backed Roland can't take this card.
TL;DR: While most Guardians have some slot issues that arise from the order in which you play your one and two-handed guns, Rogues can make good use of it fairly easily with a plethora of one-handed guns, including signatures.