Anyone have success with undersized boolits?

[CSH]

And let me stipulate that I'm talking GG bullets that are conventionally lubed and not paper patched. Had a guy on another forum say he shoots .354" boolits (intended for 9mm) down a .357" (groove measurement) bore at over 1000 fps WITHOUT LEADING! I'm thinking no way since every time I've ever fired boolits that were even a smidgen undersized for the bore my barrel looks like a corroded sewer pipe after just a few rounds. Of course, I've learned there are few absolutes in boolit shooting, but I always thought sizing to groove diameter or larger was one them unless you like scrubbing barrels.

[BABore]

I shot a bunch of 0.360 diameter GC'd boolits down the bore of a Ballard rifled, 1952 Marlin 35 Remmy. It's a 7 groove bbl that slugged at 0.3635 groove/0.350 bore. I couldn't believe my first bore slug, but should have. It shot just fine with WD'd 50/50 WW-Pb alloy at full jacketed velocity. Nothing real impressive mind you. 1 1/2 inch 100 groups and zero leading. It does much better with 0.364 boolits. My success was likey due to the more malleable alloy, driven at full pressure, in a bbl that has 0.0068 deep rifling.

[jonk]

I suspect that any results with undersized bullets are due to obduration from upset into the rifling.

I've done pretty well otherwise if I use a ballistic filler like PSB or Pufflon.