I tend to agree on this. If you need a bigger diameter bullet to seal properly just use .357 in your 9mm.Some think that a hollowbase bullet obturates more effectively to seal the bore. With a conventional jacketed bullet, I would call BS (except nobody makes them)...but for these "plated" lead bullets from Berry, they actually might.
I wouldn't bother.
Besides the obvious hole in the base...why would I choose to reload with hollow base projectiles that weigh the same?
IOW, is there an advantage?
Maybe they're longer
Interesting that the hollow base one's have the thick plating also? Makes one wonder of this option might be intended as a better fit for PCC's?
Probably for .38 Super as well, I'd guess.