From back in 2000, this is my friend Anish and I trying to break Mach 1.0 with a model rocket (class G engine - under the limit for special permits). We did not succeed, but it did reach approximately 607 miles per hour (Mach 0.79). Launch weight was about 280 grams total, 125 g of that was the engine (62g propellant), an Aerotech G80, smokeless. Initial acceleration was about 30 G's. Burn time about 1.5 seconds. 2900 feet altitude at streamer deployment. Air drag at engine burn-out was about 10G's of deceleration. All of this was measured with a homemade on-board acceleration data logger.