Ghost Recon Breakpoint works a little differently than you would expect from some games of this caliber. On the one hand, you don't exactly craft weapons in the game. Yes, you get blueprints and you pick them up, but you're not going to use them to craft weapons. Instead, they'll unlock in Maria's store. This is how the weapon system works in the game.
How Weapons Work in Ghost Recon Breakpoint
Traditionally, many players may think they are going to grab weapon blueprints in the game and then work their way through the crafting material. However, this is not the case. You'll receive weapon and attachment models in-game, but they won't let you use craft materials to craft them.
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Instead, when you get a weapon blueprint, it will unlock weapons in Maria's store. You can visit the store in Erewhon or at your resting place. You can open the store to see what's on sale at the time. The more blueprints you have in the game, the more blueprints you will get. These blueprints include the weapons and their respective attachments. Attachments will grant additional benefits and modify weapon stats.
The more blueprints you find, the more you can use higher quality weapons in the game. You can get even better weapons by upgrading the Weapon Mk skills present in your skill tree. These are important to locate as they will determine the level of quality you can buy from Maria.
It's a unique take on the homemade weapon system, but again, players don't craft them directly. They will buy them from Maria after getting a new blueprint from the map. Visit your bivouacs and Erewhon regularly to see what weapons and equipment are for sale.