5.56 & 300BLK dummy inserts

Printed on a CoreXY out of PLA+ standing up vertically at very slow speeds, ballpark 10-40mm/s to prevent being knocked over. If you continue to encounter failures consider using a brim. Bedslinger friends will probably want to go very slow and use a brim. All other settings are up to you; prints should not be undergoing much impact stress.

These inserts should fit into your empty once-fired 5.56x45mm and 7.62x35mm casings. Mine did not need anything to secure them but all chambers are different so yours might need some glue near the neck or some crimping.

When compared to live rounds I find the 5.56 insert reasonably close in profile to the usual 55gr M193. The 300BLK insert is modeled after 200gr subsonic rounds but the curvature doesn't come as close to the Magtech I use. I aimed to at least match the larger diameter subsonic rounds have closer to the neck however, so I find it's a reasonable estimate for testing magazine compatibility with subsonics. Hopefully I find time in the future to better match them.

Useful for teaching manipulation, dryfire, and training (malfunctions). Using once-fired brass grants more durability against wear compared to fully printed dummies, especially regarding the rim. Long length printed insert increases hold friction, discourages usage as projectile, and prevents setback when chambering.

Do not use as projectile.