Halo Infinite: Secret Outpost Tremonius Scorpion Gun Guide

Anyone playing on legendary will want to pick up the Tank Cannon Gun from this outpost to make Legendary much much easier to complete.

Make sure that you do this your first time at the Outpost, I am unsure if the Gun will still be at the AA cannon if you leave the outpost and come back to it later

After taking the outpost, on the Eastern edge is the ruins of a ship.
At the front of the ship are 2 AA cannons and a button, (The button is located beside the south AA Cannon and is for an easter egg that can be done before clearing the outpost, I am not sure if you need to click the button beforehand to make this show up so go ahead and activate it for the hell of it. This button will no longer be beside the cannon if you leave the outpost and comeback later)

Then, stand on the end of the barrel of the Northern AA cannon and you will see a Pick up prompt which will swap out whatever weapon you are holding.
After swapping you will now have an invisible Scorpion Cannon gun (kind of like Scarab Gun in Halo 2)

The Tank Cannon has Infinite Ammo and you can take it with you to the next mission.
It has issues shooting things lower than you are (assuming because of the way tank cannons work) so you might have to jump and then shoot, if you are on a ledge trying to take out enemies lower than you.