Made some adjustements to this style of hammer block for lower receivers (used to protect the bolt catch from being struck by the hammer when disassembling a lower). The originals were good, but i felt a few changes were needed to make them more stable.

This one goes into the magwell, and and is the more “rigid” robust option. however, it takes longer to print and removes your ability to mount the Lower on a vice block (as this uses the magazine catch). I use this if i'm storing lowers or traveling with them as it's easier to install.

You can print however you wish, i just used PLA with 100% infill. though i suspect even 15% infill is fine.

i recommend printing on the top face, …. basically facing down. you can use supports if you want some of the angles to be “prettier”, but honestly it works fine without any supports. (see my image with build plate orientation)