I had a topic on this a few weeks ago. The SG43 build has faded out of popularity, as has its build plans. Weaponeer.net has a small build section but they are light on critical dimensions. You can eyeball most of the build using the top cover as a guide, but you ABSOLUTELY MUST get the middle section correct for proper headspacing. Im not aware of any real blueprints or receiver drawings that are readily available. Id be happy to take pics on mine and send measurements, but be aware Im a garage builder and my results are far less accurate than a guy with a full machine shop.