So you've unlocked a bunch of attachments and put together a cruel instrument of destruction and mayhem, the perfect weapon, yet you can't find a way to save it as a blueprint in Call of Duty Modern Warfare 2. Thankfully, we have the intel you need to answer the question in the title. Here's everything we know about custom blueprints in Modern Warfare 2.
Saving a custom weapon blueprint in CoD Modern Warfare 2
To save a Custom weapon blueprint, all you need to do is open the Gunsmith for your favorite weapon. At the bottom left of the screen will be the option "Save a Custom Mod". Clicking this will prompt you to enter a name for the setup. This is required so you can save officially save it to the weapon itself. Once a name has been entered, save it, and you have yourself your first custom blueprint.
Your custom blueprints can be accessed exactly the same way you access a blueprint obtained from the Season Pass or from the in-game store. By opening the base weapon the blueprint is based of, you should see a list of blueprints you already have, and you should see your own custom blueprint there prior to opening the Gunsmith. Simply clicking on it will equip it, then you're done. Enjoy!
For more on Modern Warfare 2, check out guide on How to unlock Custom Loadouts in MW2 Multiplayer right here on Pro Game Guides.