ballisticxlr provides good information, however it's less about
chamber pressure and more about the pressure at the point that the gasses actually vent from the gun.
For an autopistol, that would be when the bullet leaves the barrel. For a revolver, there's some venting at the cylinder gap and then more when the bullet exits the muzzle.
I recall seeing an article some years ago about a problem with white-tail deer overrunning heavily populated areas on the east coast. Some of the municipalities in question brought in professional hunters to deal with the issue. They were using shotguns, probably to avoid issues with stray bullets, but they wanted to avoid disturbing the residents. At the time there weren't silencers available for shotguns, so the hunters used shotguns with extremely long barrels. That didn't change the chamber pressure, but it did change the pressure at the point that the projectile exited the muzzle, reducing the muzzle blast significantly.
So, pressure--yes. Chamber pressure--no. Gas venting pressure (muzzle pressure?)--yes.
Factors which affect muzzle pressure.
- Chamber pressure. The amount of pressure you start out with before the projectile starts moving. Chamber pressure is dependent on a number of things in turn.
- Barrel length. The longer the barrel, the more volume the combustion gases have to fill before the projectile exits.
- Bore diameter. The larger the bore diameter, the more volume the combustion gases have to fill before the projectile exits.
- Powder type. Different burning characteristics can keep the pressure higher longer or make it drop faster.