INDIANAPOLIS ?? Standing in a small booth surrounded by displays for rifles, pistols, holsters and other firearm accouterments, the Rev. Kenn Blanchard signed copies of his book ??Black Man With a Gun: Reloaded.?? Amid the sea of thousands of white faces that descended on this city for the National Rifle Association convention in late April, Mr. Blanchard, an N.R.A. member since 1991, offered his