Doing a Raider Melee Character using this awsome youtube build i found- https://www.youtube.com/watch?v=8SCTkpL5dk8

Looking for the sturdy raider armor legs at the moment....can't seem to find any...I found the chest and arms so far...anyone know where to go to get em? Then I'll be looking for the heavy raider armor later and was wondering where to go to find that later in the game?

It is random. If you take off the mods of Raider armor legs, then it will reveal what type of armor it is. So Muffled Raider Left Leg could turn into Sturdy Raider Left Leg or Heavy Raider Left Leg. There is also the option of using a mod to modify any Raider leg armor into a Sturdy Raider leg armor.

Not really sure, but I think Sturdy and Heavy variants of armors come at later levels.

Sturdy should appear around level 25-30. Becomes very common after that. Heavy should appear around 40-50, but might be hard to get all parts until you're like 51-52, at least that's how long it took me.

...later in the game.

In my game there are some raiders next to the water somewhere that respawn, carrying book return tokens.

Some of those tend to be wearing the attractive raider armour with the shoulder pad look and beefy legs.

I have some settlers dressed in it but i don't use the raider chests.

yeah it seems sturdy and heavy appear as your character lvs up. For a while I could not get my hands on sturdy but now it drops from just about every raider I kill.

Sturdy Raider/Leather will start to appear at around lvl 16/17. The drops are random so i would strongly suggest you do as others have mentioned and strip any mod off of the armor so you can see exactly what you have got.