Sorry. Ignore this. My M-61 shell had been swapped for M-72 shot.
this happened a long time ago, over a year in fact. Solid shot on US built/supplied vehicles (also true for British tanks armed with the 75mm) is now the stock shell, instead of the old capped shell with HE filler. Russian tanks of course still have a stock APHE shell despite historically also having a solid shot shell.
Indeed. I was wondering if Gaijin had done a stealth nerf on the NA75 as it normally has the filled M61. My irritation was due to my own inattentiveness.