I have to confess I’ve wanted to find a skinny barreled 4” 12-3 and cut it to 3”, for quite some time now.
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Aluminum frames are more likely to crack where the barrel is screwed into the frame. Both during removal/install and just during shooting. I've seen a couple of the aluminum/scandium guns crack there, and knew one guy who decided to roll the dice with a barrel swap on a Colt Agent (or Cobra, I forget which) and came up snake eyes.
You *can* chop the barrel without removing it. I think Tiger McKee did his "Choppers" that way, as did some gunsmiths back when IDPA changed the maximum barrel length from 5" down to 4". In both cases that was a chop and recrown without any additional or complicated barrel work.
Remember that there are always more gunsmiths than there are people qualified to be gunsmiths. Choose carefully.