Large (approximate to 45.4kg) hemispheres of C-4, detonated on the ground, were instrumented to measure blast parameters at scaled distances between 0.53 to 1.78mkg(-1/3). The results from free-field and reflected pressure gauge measurements made inside and just outside the maximum extent of the fireball are presented. They show that the predictions from a particular table for scaled TNT charges are broadly consistent with the time-of-arrival, initial peak pressure, positive duration and positive impulse measurements. However, this agreement is poorer through the location of the primary and secondary (delayed) fireball (0.71-1.48mkg(-1/3)), but better closer in and further away. Additionally, for individual detonations with closely located gauges, significant variations between peak pressures and times-of-arrival are measured. This suggests a strong effect from the interface instabilities present in the near-field.