Drew;
I have seen those feathered edges on plastic shells which were fired in correct chambers so the hull did not even enter the cone, much less the bore.
I read Bell's report at the time but don't recall how many shells he actually fired, in my "Opinion", not hear enough.
The greatest work which has ben done on this question was done by the British with the introduction of the pie/fold crimp shells in the late thirties. It was delayed a bit by a "Little Domestic Spat" going on known as WWII, but was completed shortly thereafter. This was all of course done with paper hulls loaded with card & felt wadding.
What Bell truly did was to confirm that what had been common practise across the pond for nigh onto a half century would work on this side, even with plastics.
