Note: measuring the sound levels from firearms require special equipment capable of measuring sound levels of max 185 db and impulse metering .
Even using the state of art equipment’s and following the MIL-STD-1474D/E (US military standards there are several factors that might influence in the measurements as:

1. Ambient conditions, temperature, humidity and barometric pressure

2. Type of firearm, length of barrel

2. Type of ammunition – powder type, bullet weight etc. (muzzle pressure and amount of unburnt powder)

3. Standard deviations in test set up and measuring equipment.

We conduct our testing and measurement in the best way to our knowledge and so far we base our acoustic data on more than 3000 measurements.

Based on above we claim that the uncertainty in the data  lays in the area of +/- 1-2 db