I edited it to 9 so a newbie doesn't pick up on it.
Obturation of cylinder throats in a 45 Colt revolver shooting within SAAMI pressures will not occur using hard cast bullets. With the common BHN 16 bullets, you need almost 23,000 psi for the bullet to start to upset outward in diameter. BHN 12 needs about 16,800 psi to upset. For 12,000 psi to cause obturation, you need a BHN that does not exceed 8.5. So, switching to softer bullets, perhaps swaged bullets, will allow upset to stop gas from escaping forward, which slows the build-up of pressure. But if your bore is rough, the soft bullets can lead badly. Without soft bullets, you will have to wait for the bullet to reach the throat to obturate the bore by virtue of its diameter being greater than the groove diameter of the barrel since the harder bullet won't upset.