This is a chamber flag I designed in Tinkercad based off an existing one that came with one of my guns. It is NOT meant to take the full weight of the bolt pressing against it. At the range, I insert it thru the ejection port and down thru the magwell after the bolt locks back after the last round is fired, when the range goes cold. It makes it easier for the range officers to see that the bolt is locked open and clear. Print 100 percent infill and use PLA + or something a little tougher or more flexible than regular PLA. Prints in 22 minutes on my Ender3 using CHEP'S extra fast Cura profile.

Update: I added a 2nd version that has a slightly curved "tail" to make it easier to get in the magwell

Creality

Ender 3

No

No

100