NOTE
Sometimes the brass case itself will not feed. Some of my brass - I believe the ones used in my cmmg conversion - have expanded at the rim more than the ones used in my 22 pistol. In this case, the brass ITSELF is the problem. Test the brass first if you are having feeding/seating issues.

UPDATE 01/18/2021

This version works the best for me!

Some of my TPU came out nasty near the tip and I don't want to trim and snip 20 of these so I made a 2 part version. A TPU sleeve which you push in first with the bevel UP. Make sure about 2mm is showing. Then push in the PLA insert. It has a bulb section which almost makes it permanent. The PLA prints much better and shouldn't need trimming. I cleaned my brass with a q tip and alcohol first.

I used the size in the comments but I had 2 issues because I printed this out of TPU (I wanted it somewhat malleable).

1) I couldn't get the damn thing in because it was so snug the air was trapped so I added a groove to let the air out

2) the part not in the case was just a tiny bit too large and it wouldn't extract so I shrunk that section a little bit

3) because of TPU tolerances the entire thing is a little smaller. If it's too small just increase it a little at a time. 101% or 100.5% maybe. Have a rod handy in case it gets jammed.

so now it works for me and if you have a hard time inserting it into the case, just wipe the flat bottom with a little oil and it should slide in. I don't THINK you need to glue it or anything, it seems snug to me. No extraction issues for me.

Prusa

i3 MK3

No

No

0.2

70%