The other day we put a bunch of recessed lights in a house. The guys didn't look at the labels on the bulbs and some different type bulbs were used. Most were 120 volt BR40 65 watt, a few were 130 volt BR40 75 watt, The 65 watt bulbs were much brighter. I know the 130 volt bulbs won't put out 75 watts unless the voltage is 130, but the difference was huge, the 75's looked like 40's compared to the 65's.

Why was the dif that large?