A quick-handed NYPD sergeant stopped a violent felon from shooting him in the gut by jamming his ring finger under the hammer of the felon’s .38 revolver, cops said today. Sgt. Michael Miller and Officer William Reddin were on patrol when they noticed a livery cab speeding eastbound on Quincy Street near Malcolm X Boulevard at about 4 a.m. today. The plainclothes cops pulled the beige Lincoln Towncar over, but when they walked up displaying their shields they noticed that one of the passengers in the back seat, Eugene Graves, was making suspicious movements near his waistband.