This is one of the key tests in rating an explosive. The value is expressed as so many meters per second (mps) and is density dependent. Some values are: PETN 8,300 mps at 1.773 g/ml, RDX 8,700 mps at 1.770 g/ml, HMX 9,110 mps at 1.89 g/ml, TNT 6,826 mps at 1.636 g/ml, Nitroglycerin 7,700 mps aat 1.6 g/ml.