US WW11 90mm M82 projectile

i have a US WW11 90mm APHE M82 projectile, it have a very large base thread, much larger than for a M68 fuze, maybe some kind of a
base plug with a tracer or the base fuze ??? no picture at this time , anyone have some drawings or info. joe gatz CWO4 RT

This from TM 9-1901, Artillery Ammunition (1944) might explain what you are seeing:

any have a drawing of the plug and base fuzeM68 with all the dimensions. joe gatz