Fuse doesn't blow when overpowered?

I have a fused distribution block with 100 amp mini anls, however I'm running a skar rp 1500 tuned via scope, running about 1550-1600 watts RMS 41v output from amp, is 100 amps at 12 volts is 1200, why isn't the fuse blowing, also could it be resticticting power to the amp? Does the resistance rise alot past the 100 amps meaning I'm losing power, but it's not quite enough to blow?