[Michael Chandra]

I read the 5P as inaccurate hand cannon stats, not Flechette stats. That section simply means to me that the Roomsweeper uses Heavy Pistol rounds explicitly.

Note that the Slivergun mentions it uses flechette rounds in its table-stats (f). It's the only weapon doing so.

[ZeroSum]

Heavy Pistols are 3P, with the exception of the Ruger Super Warhawk, which is described as "shiny and chrome and makes holes the size of a troll’s fist straight out of the box", and the Ares Viper Slivergun, which uses "metal slivers that count as flechette ammunition and are bought as such, but they aren’t interchangeable with any other flechette weapon". Both of these weapons are +1 DV over the other Heavy Pistols.

This is similar to the Remington Roomsweeper being the only weapon rated at 5P, whereas all other shotguns are 4P.

I believe this has been discussed in several other threads, including the change blindness thread, as flechette ammo does -1 DV unlike the Slivergun (and potentially the Roomsweeper, depending on your reading). I don't think there is conclusive evidence either way, but based on the Slivergun I lean towards the Roomsweeper having +1 DV as Flechette was +DV and +AV in past editions.

[Michael Chandra]

The Roomsweeper doesn't have flechette ammo as base damage: Flechette notation is (f), and where the Slivergun is 4P(f), the Roomsweeper simply is 5P.

[ZeroSum]

The Roomsweeper doesn't have flechette ammo as base damage: Flechette notation is (f), and where the Slivergun is 4P(f), the Roomsweeper simply is 5P.

Partially incorrect. Hey, I get to correct MC for once

p. 262, Flechette Ammo
Note that (fl) is the abbreviation for this type of ammo.

And yes; the Slivergun does specifically state that it uses Flechette, but the description of the roomsweeper indicates that it does, too. As far as I can tell, the only difference between the Roomsweeper and the other shotguns when it comes to Damage Value is that the Roomsweeper mentions flechette and heavy pistol rounds.

Heavy pistol rounds are not inherently more damaging than shotgun slugs (shotguns with slugs are 4P, most Heavy Pistols are 3P with the exception of the Slivergun and the Ruger Super Warhawk). Given that both the Roomsweeper and Slivergun mention Flechettes, and Flechettes in past editions were +1 DV, it is therefore possible that the profiles for the Roomsweeper and Sliverguns were written before ammunition stats were finalized.

Bottom line, ammo types for some weapons are borked.

[Michael Chandra]

The Roomsweeper doesn't have flechette ammo as base damage: Flechette notation is (f), and where the Slivergun is 4P(f), the Roomsweeper simply is 5P.

Partially incorrect. Hey, I get to correct MC for once

p. 262, Flechette Ammo
Note that (fl) is the abbreviation for this type of ammo.

That's after errata, though. In unerrata'd CRB, "The payload of a flechette (f)" on p262 and "4P(f)" on p255 both use (f), errata update both (probably because (f) is reserved for fire). Note that the errata do not mention changing the Roomsweeper's damage code, which still is 5P, not 5P(f) or 5P(fl).