To unlock both the Handcannon and the Chicago Sweeper in Resident Evil 4, you need to undertake specific actions on Professional difficulty mode. Below is a detailed guide to walk you through the requirements and steps necessary to obtain these powerful weapons.

Unlocking the Handcannon
1. Complete a Fresh Run: You must finish a new playthrough of Resident Evil 4 on Professional difficulty. There is no need to achieve a specific rank; any rank (A, S, etc.) will suffice.
2. End of the Game: Successfully reach the end of the game to automatically unlock the Handcannon.

Unlocking the Chicago Sweeper
Once you have the Handcannon, you can then pursue the Chicago Sweeper:

Method 1: Achieving A or S Rank with the Handcannon
1. Use the Handcannon: You must utilize the Handcannon during your playthrough on Professional mode.
2. Achieve Rank: Earn at least an A rank by the end of your run. Focus on optimal gameplay to defeat enemies quickly and efficiently to meet the criteria.

Method 2: Alternative Unlock
– Complete the Leon “A” Kennedy Challenge or finish the main story once on Professional with at least an A rank. This serves as an alternative method to unlock the Chicago Sweeper.

Requirements and Tips for Achieving the A Rank
To successfully achieve the A rank and unlock the Chicago Sweeper, keep the following points in mind:

1. Time Limit: Complete the Professional mode campaign in under 7 hours. This time constraint is critical for obtaining the A rank.
2. Utilize New Game Plus Modes: Consider using the Infinite Rocket Launcher and other powerful weapons available in a New Game Plus run, as these can greatly streamline your run and help in managing the time limit.
3. Weapon Strategy: Employ the Infinite Rocket Launcher for significant damage during encounters, while you can use the Handcannon for quicker eliminations. Having a pistol as a backup for close combat situations is also recommended.
4. Saving Often: Since Professional mode lacks autosave features, make it a habit to save at strategic points to prevent losing significant progress.

Upgrading the Chicago Sweeper
– Infinite Ammo Upgrade: To gain infinite ammo for the Chicago Sweeper, you must fully upgrade the weapon first. Then, purchase or use an exclusive upgrade ticket from the merchant. This ticket grants infinite ammo either immediately or after completing the necessary upgrades.

Summary Steps
1. Finish a fresh run on Professional difficulty to unlock the Handcannon.
2. Use the Handcannon and aim for an A or S rank during a Professional run.
3. Complete the Professional mode in 7 hours or less to qualify for the Chicago Sweeper.
4. Fully upgrade the Chicago Sweeper and purchase or utilize an exclusive upgrade ticket to obtain infinite ammo.

By following these steps diligently, you’ll successfully unlock both the Handcannon and the Chicago Sweeper, significantly enhancing your arsenal in Resident Evil 4’s Professional mode. Good luck, and enjoy your powerful new weapons!