I just measured the core depth of a 1975 Estes B14 and a 1990 B8 and found them to be within a hundreth of an inch of each other (0.68" from the casing edge, not the nozzle exit, though they appeared to be the same). The throat diameter of the B14 was 0.17" vs the B8's 0.145", so they were already de-tuning the B14 at that time.

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Roy
nar12605