After a bit of trial and error I found that my M-64 of 1949 or 50 vintage really prefers boolits sized .323 (RCBS 32-170FNGC.
My dies are an older Lyman set and I found the expander button only measured .318 which led to collapsed cases when seating the .323 boolits.
The available solution was to get an RCBS expander/ flaring die with the expander dimensioned to handle .323 boolits. This solved part of the problem .
The Lyman seating die however was tight enough that it promptly removed the flare and sized the brass almost back to where I started again resulting in collapsed cases once more.
I measured the depth in the seating die to the crimp shoulder and marked a dowel at that depth. The dowel was split lengthwise for an inch and a bit in a band saw to take a section of 320 grit emery paper which was slid into the slot and wrapped on the dowel to a tight fit in the die.
Chucking the dowel in the drill press and with oil in the die I hand held the die and proceeded to lap it out, finishing with a 600 grit polish. By not going deeper than my mark on the dowel I was able to retain the crimp shoulder.
The end result is a die that works and my rifle likes the results. The whole process took less than an hour including a couple of tests which indicated more metal had to be polished out of the die.
If I had better sources of getting reloading tools quickly this probably wouldn't have been done at all but if you have similar problem the process works just fine.