Tacfire UP02: Starting another AR-15 build will always come down to how I want to configure my upper? Do I want a prebuilt upper receiver, or do I want the satisfaction of piecing together something unique? If you are the second option, I encourage you to check out this great option from Tacfire. Machined from forged 7075 T6 aluminum and featuring some interesting design choices. Tacfire has made a great-looking slick side upper receiver ready for your choice of parts to finish the job.