All I can say on this subject is that the only clipped ammunition I saw for the M1 during my Army service was Ball M2, AP and Blanks. The onlty place we were issued blanks in M1 chargers was in basic training and AIT. The only blanks I ever saw after training were in boxes, not in clips. I never saw any tracer, incendiary, APT or API in clips. For some reason, in the Reserve, we saw quite a bit of AP on clips - perhaps more than ball - and it was all old, from WWII. This was in the early 1960s, when I was finishing my second enlistment.
Of course, I was a peace-time soldier, and my experience with the more exotic types of ammunition is limited. Further, the majority of my Regular Army service as a Personnel Specialist assigned to Command Headquarters (Yukon Command) and quartered with the Signal Company. I was only an infantryman for a short time, and being peacetime, was disqualified when I took my overseas physical for USARAL, since my eyes were no longer 20-20. So. again, my experience is much, much more limited than that of combat verterans.