September 28, 2004 -- JACK Daniel's has sparked outrage among serious drinkers by unceremoniously lowering the proof of its famous Tennessee Whiskey from 86 to 80. The change — which means the hooch has 3 percent less alcohol — has riled those still smarting from the "betrayal" of 15 years ago when the company lowered the strength of its 90-proof, 138-year-old original recipe, to 86 proof. Frank Kelly Rich, editor of Modern Drunkard magazine (and a contributor to The Post's Sunday books section), has taken up the cause along with "alert drunkard" Chris Sharp, who was apparently the first to notice the switch. Sharp has started an online petition and boycott with the magazine's backing "designed to right this grievous wrong." Distillery rep Roger Brashears told us, "We researched it and decided the majority of people wanted a less potent drink." Rich writes, "Jack Daniel's is, of course, a private corporation and they can do whatever the hell they want," but called the alcohol dilution "unfathomable blasphemy. They can lower the proof to zero and call it lemonade if they like. But that doesn't mean we have to drink it."