the 1st time I took my AR to the KHSC rifle range, dutifully in compliance, with only 10rd mags, I noticed one AR dude to my left with 40rd Pmags no hassles, another AR guy to my right with the USGI patina'd aluminum 30rd mags, of course, all only loaded to 5rds. I felt pretty stupid. However, at KHSC, I still use the 10rd mags, but only because with the bipod, to clear the bench. I go elsewhere to shoot rifle with the 30rd, 40rd mags if I have that need. I see AK guys pretty regularly at KHSC with their 30rd banana mags, of course, ostensibly loaded with 5rds only.
just my observation, not inferring anything from that.