For a coverage option to be worth it, it has to be able to hit the target for decently more than Head Smash. That in turn requires the move to have a decently high BP already
2x Resisted Head Smash has a BP of 112.5
4x has 56.25
So usually, Head Smash has to be a 4x resist, or a 2x resist and the coverage option super-effective with enough of a BP difference
252+ Atk Choice Band Tyrantrum Head Smash vs. 252 HP / 144+ Def Hippowdon: 134-158 (31.9 - 37.6%) -- 0.1% chance to 3HKO after Leftovers recovery
252+ Atk Choice Band Tyrantrum Earthquake vs. 252 HP / 144+ Def Hippowdon: 119-141 (28.3 - 33.5%) -- 95.5% chance to 4HKO after Leftovers recovery
The fang moves aren't really worthwhile coverage unless they strike a target for 4x damage given their low BP, and many Fang targets are probably neutral anyway and have to be caught on the switch
252+ Atk Choice Band Tyrantrum Outrage vs. 252 HP / 144+ Def Hippowdon: 214-253 (50.9 - 60.2%) -- 89.1% chance to 2HKO after Leftovers recovery
-1 252+ Atk Choice Band Tyrantrum Head Smash vs. 252 HP / 240+ Def Landorus-T: 199-235 (52 - 61.5%) -- guaranteed 2HKO after Stealth Rock and Leftovers recovery
252+ Atk Choice Band Tyrantrum Head Smash vs. 252 HP / 56+ Def Gliscor: 274-324 (77.4 - 91.5%) -- 31.3% chance to OHKO after Stealth Rock
252+ Atk Choice Band Tyrantrum Head Smash vs. 248 HP / 0+ Def Mega Scizor: 262-309 (76.3 - 90%) -- 18.8% chance to OHKO after Stealth Rock
As far as Dragon STAB, I could see some merit in it, mostly because it's Tyrantrum's second strongest move in terms of BP. On top of still being hard neutrally to switch into barring Fairies and Steels, Outrage's power is usually enough to beat the few targets that the fangs might've earned their keep against
252+ Atk Choice Band Tyrantrum Outrage vs. 252 HP / 252+ Def Chesnaught: 193-228 (50.7 - 60%) -- guaranteed 2HKO after Stealth Rock and Leftovers recovery
252+ Atk Choice Band Tyrantrum Outrage vs. 252 HP / 252+ Def Garchomp: 458-540 (109 - 128.5%) -- guaranteed OHKO
As far as his own coverage, Tyrantrum's concern isn't "coverage that can KO" as often as it is "coverage that will put them in Head Smash range", or coverage that beats something he can't get in that range. For a Band set, I foresee something like this being his best option
Tyrantrum @ Choice Band
Ability: Rock Head
EVs: 252 Atk / 4 SpD / 252 Spe
Adamant Nature
- Head Smash
- Dragon Claw/Outrage
- Superpower/Earthquake
- Toxic/Superpower/Earthquake
Outrage bops most targets with a Base 120 STAB move, while also having a coverage move for one or two bulky Steels/Rock Resists (whatever they might be). Either run both, or Toxic to just deal with the most persistent ones or soften them up for a teammate without worrying about prediction.
Head Smash's obscene power leaves very few cases where Tyrantrum's concern is "Should I Head Smash?" as opposed to "How do I get off a Head Smash?"
