I wonder if that is what he means here by a 30 round clip -- two 15s taped together.
That wouldn't make any sense either. No place to tape them except on the ammunition itself, and then you couldn't get it into the magazine. Maybe he meant two 30 round magazines taped together. That works, because a 30 rounder is so long that taping across the bottom of the mag, with each reversed relative to the other, leaves enough "free" to insert into the mag well.
bflr