Probably not optimal; But viable?

[Rtgamer]

Im going on an adventure! Starting in 3weeks.
Mountain Dwarf / Kin to another PC
Rolled stats / 8 10 14 15 16 18 and a free feat.
We all (the 5 of us) start out as 3rd level PCs That’s 3 Elfish Bards and a Mtn Dwarf Fighter my cousin Ringo The Cute who plays drums for their traveling band. So
I am going to travel with them. My name is Glover Sparklecheese. an Urban Bounty hunter, I want to use a heavy Xbow and the piercer feat with 1st lvl in Fighter and archery style. So that 18 is going into Dex. Next ASI probably SS. Lvl 2&3 are Rogue. 16+2Con 15+2+1Str 14Cha 10Wis 8Int.
Continuing on to Swashbuckler5 then Samurai5.
Hoping through RP to attune with a +Heavy Xbow that helps with loading or ammo properties.. xbow expert maybe if I must. Studded leather with helmet,& rapier
I want strong range attack fast melee and competent grapple abilities. For me the start stats and 3 ASIs by lvl10 or 4 by lvl11 is solid
What say ye Sages of Scuttlebutt?

[RogueJK]

Sure, it's viable. It's tough to make a non-viable 5E build, especially with stat rolls that good...

But since it seems like you're wanting to focus on ranged attacks with a Heavy Crossbow, going to 5 levels of the Swashbuckler subclass doesn't get you much of anything there, other than +2 to Initiative. Swashbuckler is a melee-focused subclass.

You'd get more as a ranged crossbow user out of 5 levels of a different Rogue subclass, like Scout for two additional skills and reaction ability to move away from melee enemies, or Phantom for a bit of extra damage and an bonus rotating skill proficiency, or Thief for greater climbing/jumping ability to combine with your high STR/Athletics.