The first time you can get this is when you get to the town of Valentine.
Head to the gun smith, and select a weapon (I went with my sawed-off)
Go down to components, and clean your weapon.
Now buy one from each section of the components option.
For the sawed-off there are three upgrades to buy: iron sights, stock and wrap. You will need about $30 to do the cheapest of each upgrade.
You don’t need to worry about the Styles or Ammunition menu.
If you want the achievement but don’t want to spend the money, just save, complete the upgrades and load.