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Old January 3, 2021, 12:31 PM   #9
P Flados
Senior Member
Join Date: January 8, 2017
Location: Wilmington NC
Posts: 170
The point about pressure and gas volume matches up with my understanding of the the sound level.

However, for guns other than revolvers, it is muzzle pressure and not chamber pressure. I will expand on this below. For a revolver, it is a mix. The sound from the cylinder gap is a function of pressure in the gun as the base of the bullet exits the cylinder, and the sound from the muzzle blast is a function of muzzle pressure.

Quickload calculates both chamber pressure and muzzle pressure. Faster burning powders reduce muzzle pressure. I ran 3 loads with just enough powder to push a 240 gr bullet to 1200 fps from a 6" 44 magnum using a 1.61" AOL.
  • H110, chamber pressure 23818 psi, muzzle pressure 6879 psi
  • HS6, chamber pressure 29117 psi, muzzle pressure 5183 psi
  • Universal, chamber pressure 36490 psi, muzzle pressure 4335 psi

FYI, assuming 1" of bullet travel for the bullet to leave the cylinder, all of the above loads have about the same pressure (~22000 psi) pushing gas out of the cylinder gap.

Smaller cases also reduce muzzle pressure. Here is a 44 SP with a shorter AOL (1.3") loaded with the same bullet and to the same velocity. Note that the load below is dangerous and only presented as a theoretical example. As you can see, the chamber pressure went up and the muzzle pressure went down.
  • HS6, chamber pressure 45681 psi, muzzle pressure 3479 psi.

Also, some loads burn 100% of the powder inside the barrel and some do not. For example, a 240 gr JHP 44 magnum with a case full of H110 burns only around 80% of the powder in a 6" barrel. To me, loads that burn less in the barrel (i.e. more outside) seem a lot louder.

Last edited by P Flados; January 3, 2021 at 12:50 PM.
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