I think he had two 15 round clips taped together for rapid changeout, thus they may be referring to them as 30 round clips.
Hi!
As far as I know, and I maybe wrong. No mainstream manfacturer, there may be some, but no “name” manufacturer, produces a 15 round clip. Besides that, no ar-15, That I know of, is clip fed. I’m sure someone can google something and tell me I am wrong.
WHEW!!!
Oh, no one produces 15 round magazines either. AFAIK