I'm sure this question has been asked before but atm I don't have time to search for it (I'm leaving for work momentarily).

Essentially the title explains my question. What are the best ranged carries and why?

Currently I have been using Tristana but I'm not sure if I should check out the other carries. Is she a viable ranged carry?

When I was just starting, I loved tristana... she is a very solid ranged carry and still viable... ashe is often considered a great ranged carry because she has a stun that helps the team... other than that Twitch is a powerful carry but has a very different playstyle than many others, focusing on positioning and ganking.

If you like skill shots, AD ezreal is one of the most powerful physical carries, especially with his recent buff.

Tristana is powerful throughout the game, but other options in ranged carries include Sivir who has a very powerful early game and a lot of pushing potential, but strongly tapers off late game into a support role, and corki who is uncomparably the strongest ranged dps character but has a weak early and mid game (he is also likely the hardest character in the game to master)

I haven't played Twisted fate but he is a very powerful ranged dps, has a stun, and adds team utility...

Try to avoid teemo, he can be a carry but is generally outclassed by all of the above

Ashe is the safest for any given game, pretty much the other choices rely on team compisition.

Ezreal, Tristana, and Corki are strong ranged champions. Ezreal has tremendous damage output with Lichbane Hybrid builds. Tristana is great when built near pure AD, rather "meh" if AS stacked. Corki benefits rather well from the hybrid items and TriForce or Lichbane depending on how hybrid you build.

Ashe is a bit "meh" outside of supporting other lanes with ECA during the majority of most games. That support is a very good reason to use her, as she progresses into being a good Carry late game from being an ECA Stun and Volley Snare bot early and mid game.
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Tristana rapes face with a combo of last whisper, infinity's edge, and Frozen Mallet, if the opposing team has built more hp a madred's bloodrazor tears them apart.

I'd say twisted fate. Has a slow, AOE, stun, skill shot, 1.5 second teleport to anywhere on the map, reveales all enemies, and not to mention 180+ magic damage every 4th hit.

It all depends on the build and how fed you are, but overall I tend to do better end game with TF than with trist/ashe and other ranged carries.

Sivir can be absolutely overpowered in a push team. She stacks damage and takes advantage of the buffs provided by other champions spells and aura items.

Jana's shield + Aegis + Stark's + Taric's Ult + Nidalee or Ezreal's attack speed buff + the ability for her attacks to bounce = Pain.