It's not the caliber which makes it an assault weapon; it's the design.
My H&K .223 is an assault weapon.
I asked this question to the person who made a statement that sounded odd to me, and he/she then replied:
"Acually I meant 5.56 I was thinking something else when I wrote this.
I gotcha tho--thanks...I hardly see my Rem Model 7, bolt-action (.223) as an assault rifle! I do enjoy taking it outside on the range tho.!!!!