Extension allows for use of a longer inner barrel, or mounting a silencer or flash suppressor.
At both ends there is a 14mm left-hand thread.
There is a 1-layer-thick layer in the bottom of the top part. It helps to create the smaller circles, but you can easily remove it with a drill bit when it's done.
I used rafts, but it's not necessary.
Obviously, it's the best in ABS, but it is perfectly usable in PLA.
barrell_extension.stl | 540.4KB |