Thanks Rob, I will be testing my Bam B50 multi shot breech with sidelever.
PLA is stiffer than either ABS or PETG. I've made and used several PLA breeches on Armada/Marauder based rifles at up to 180fpe.They performed fine. Transfer port tubes were made of brass. PLA does not like high temperatures. I switched to aluminum using a lost PLA process once the design was to my liking.For something like a bullpup where the breech does not need to support the barrel or scope, I would not have a problem keeping the plastic breech. PLA is fine, but ABS or PETG is probably better for longevity. Any (PLA, ABS, PETG) can work, just design accordingly.I have found that I get better results doing thread forming in PLA rather than thread cutting on small fasteners. Use the appropriate thread forming hole size and then form the threads using a lubed screw.
Scott, I'm curious about your approach to the lost PLA casting. What do you coat the PLA with? Do you burn out the PLA or let the aluminum do that?Nice results!
...You are quite right in making all the parts seeing high pressure air out of something much stronger....
I was hoping to be lazy and 3D print the pattern.