AR 15 UPPER vise blocks - one uses a combination of 3/8" and 1/4" bolts, the other uses all 1/4" bolts. The default print orientation is recommended to avoid layer separation when in use. I printed with 12 walls and 50% infill and it is really hefty. Enjoy! The original design was downloaded a few years ago and has since disappeared; so I don't know who originally designed this. I have modified it via redesign of the 3/8" (vertical) bolt holes and added a 1/4" bolt hole design, and cleaned up the STL. The 3/8" vertical bolts are inserted from the bottom. The thread portion of the 3/8" holes may require thin walls to be printed. A 3/8" smooth rod may be substituted, depending on your needs.

Update - added a better channel for the gas tube; now, a fully assembled upper can be placed on the vise with clearance for the gas tube.