it’s not necessarily with a bullet. Most improvised attack drones drop explosive payloads, since it’s both simpler to set up and simpler to use. Outfitting a drone with a gun takes making a complicated system for aiming it, while a payload drone just needs some 3d-printed parts, some extra wiring, and usually just a single servo.
GarandThumb did some tests in a video a while back. IIRC he did both choked and not, along with different types of shot and slugs. everything but birdshot was pretty effective out to a couple dozen yards? I’ll track it down and drop a link after I’ve rewatched.
EDIT: so in “How Deadly are Shotguns”, they fire 00 Buck unchoked at around 7 - 8 minutes, and it is still getting a drone-sized spread at 21 yards. In the video “How Far are Shotguns Deadly? BirdShot, Slugs, and 00 Buckshot”, we see birdshot and 00 Buck used choked all the way out to 120 yards. From my perspective, birdshot and 00 buck start having a potentially viable spread at 50 yards (slowmo spread footage at 14 minutes).
I think that most likely, a pellet size between birdshot and 00 would be better, to provide that peppering effect while still delivering greater impulse per pellet. Garand also mentions in the first video that chokes can actually cause wider spread when used with shot, so unchoked shotguns may be ideal for an anti-drone function.
prior comment edited for ya.