What weapon upgrades make their corresponding proving ground significantly easier

In my experience, you need the upgrades to get first. I was only able to get second without significant upgrades.

The upgrades that make this challenge easy:

• 55% faster reload: Since you move so often in the challenge, a larger clip doesn't really help.
• 50% damage: Wider attack spread makes the challenge harder.
• 55% faster reload
• 50% damage
• Bolts Seek Out Foes: Ricochet doesn't help, homing is an obvious benefit.

In actuality, you can get first without the Tier 5 upgrade and simply rely on the auto-targeting the game does once you are close to the targets.

You should head straight to the middle to start off with, and take out as many of them as you can. After that you should go the squirt spawners, and finally move on to the towers. I'll also point out that one charged machete throw will destroy a tower in one hit, which makes it preferable over melee since they cower after being attacked. Any coward you missed at the start that you come across while taking care of the spawners and towers should be destroyed on the spot, and the rest should be hunted down after you take care of the towers.

For upgrades, you should use the tier 1 serrated edge upgrade, it's effects not only makes it harder for the squirts to get away, but could still result in them dying if they do. It's effects are:

Attacks cripple foes
Attacks deal damage overtime

For tonics, you should equip Werewhisky, and suicide off the edge of the map until it activates. Make sure you do this before picking up the Machete:

+100% Critical Hit Chance
Note: Active Only When Below 33% Health

You may find this video helpful as well if you prefer visual aids, which uses the same steps outlined by DMA57361: