How do you get more access to better weapons?

You can get better weapons by upgrading your Workbench facility. This unlocks the higher ranked weapons that you can craft using resources found in various locations, from expeditions, scavenging outposts, etc. Once a weapon is crafted, it is permanently yours; you can switch it from your weapon wheel from any workbench. Unlike in FC5 however, you can't customize your weapons at all.

Some-elite ranked weapons require materials from Monstrous Animals though they have the same stats as their counterparts that only require ordinary parts.

You can buy an Elite-ranked weapon even if you haven't unlocked the necessary rank yet by using Prestige Points. You can buy Prestige Points using real money or picking them up from Treasure Hunt locations. The amount you can get from Treasure Hunt missions are small and finite. Take note that there's no Prestige-exclusive weapon; you can get them eventually by upgrading your homebase and your workbench. Prestige weapons will just allow you to get a weapon or vehicle earlier than necessary, without the hassle of farming for the necessary materials.

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