Larry,
Just looked at my 12 GA Repro cones. They do look to be shorter than what I would expect, Looking straight on they appear as just a dark somewhat thick line. Angling reveals the taper. Tried to measure length with a bore micrometer without success. My guess is no longer than 1/4" if that.
An Arrieta 12 sitting next to the Repro has cones at least twice as long as the Repro.
Bob Jurewicz