Thoughts

Overall very fun, the most important thing to keep in mind is how weapons are proccable as offhands, especially with your ultimate. you can make some insane combos

You go through your ammo decently quick, especially if you're casting abilities. So if you mess up an order you can remedy it

Runaan's is 100% core

Combos

Calibrum Infernus is really fucking good combos. Open with infernum q, marks all enemies with calibrum. Switch to calibrum them to auto them all and when you do it attacks with your offhand, dealing massive damage cause of the infernum aoe overlapping

Calibrum gravity cannon ulti combo is really good. Ulti with calibrum to mark a bunch of enemies. Auto with calibrum to consume the marks and hit them all with gravity to slow, then swap to gravity to root them all

Best dps by far is severum boomerang. Hitting enemies with boomerang as offhand gives you glaives around you. The glaives deal bonus on hit damage when attacking with boomerang. Severum single target damage is insane, and then you can switch to boomerang to deal even crazier single target damage. and the lifesteal turret heals you making you basically un 1v1'able. If you have high enough ammo you can get FUCKING 14 or 16 GLAIVES WHICH FUCKING oof the damage was insane

Gravity infernum is also really good for proccing the root

The ultimate opens up huge combos with weapon that attack with offhands.

Orders

For late game you 100% want the order to be

calibrum, gravity/flamethrower, gravity/flamethrower, boomerang, severum.

You want to blow all the ammo on your other weapon once you arrive to boomerang so you can get lifesteal to survive fights and then swap to boomerang for damage. and you can open in a teamfight with a low ammo calibrum gravity/flamethrow for a quick swap off and good aoe damage

other combos i havent tested yet but severum gravity is ass avoid it at all costs.