The guns are designed in AUSTRIA.
Ya Know? EUROPE.
Where NATO spec ammo is 124 grain.
115grain 9mm ammo exists so American bullet manufacturers can make 11 bullets for the same amount of metal they would need to make 10 124gr bullets. Cheapskates. Nothing magical about 115s. The gun was designed around 124s.
Glock tweaked the springs and ejectors so the Gen4s I have shot, at least, don't BTF.
Just shot a State Steel Challenge Championship with my G34Gen4. Used Atlanta Arms Blue Box 115s (gun was designed for 124s; didn't say I never shot 115s myself. With the current ammo drought I like everyone else will take what I can get when I can get it.)
Functioned flawlessly and no brass in the face.
Are the ones still causing the problems ones that have not received the updated parts?