Argon Scope can be swapped for Bladed Rounds depending on your personal preference.

Argon Scope:

• Full Zoom +60% Headshot Damage
• Headshots = 115.5% Critical Hit Chance
  (Since it's a sniper rifle, you want to go for headshots with full zoom anyway to get the bonus damage and you'll get a more consistent critical hit output thanks to Argon Scope.)

Bladed Rounds:

• 6.8x Critical Hit Multiplier on Kill
  (With [Bladed Rounds] you'll have a potentially higher damage output, BUT you'll need to kill first to activate it AND have a 25% chance of your shot NOT being a critical hit that would benefit from the higher multiplier, making you more RNG dependent.)

Side note:
Since you'll only have 1 bullet in the chamber, your reload speed will become your fire rate and since reloading is very fast, it'll feel like you have an endless magazine and you'll never have to worry about reloading ever again.