Dead Space 3

Ok, go to any bench, slap together a weapon out of any parts you have. Make a blueprint out of that weapon, and then share it with your friend. Simple as that.
To share your blueprint, go to the blueprints page, where all of the blueprints are listed. Go down to the one you just made and hit "X" to share it

NOTE: This will not work with blue prints made out of pre-order weapons or downloaded weapons.

This is really easy. All you have to do is make the most basic weapon. Just do a standard frame or what you feel like and a top tool. Don't have any special parts like the MK II/V. No pre-order weapons or special unlocks and no DLC. If by chance your with another that has not gotten far in the game or hasn't unlocked certain pre-made blueprints then you can trade them too.

Just go to any bench construct the weapon go into blueprints and hit "X" for share. Soon as it's sent it will unlock.

If it does not allow you to trade then you put in an item that's not allowed.