It may not be a vehicle to-hit chart/counter. Look at 14.2.1 on p. 38 of the rules. The counter has H (HEAT symbol) and SR (at center, top, of counter).
Our M113s, M2/3, M60, M1s all had smoke grenade dischargers back in the 1980s. I'm in Reserves now and the vehicles are still equipped w/ them. Common tactic when fired on was to pop smoke and slam into reverse or drive up to a breach location, pop smoke, dump out the infantry under smoke concealment, then use the AFV for suppression. I'll work on some "house rules" and post them.