MIKE: Isn't planning on the length of the Breechplug supposed to be something you do in prepartion for fitting your lock and locating the eventual position of the vent? We know that a plug does not have to be several inches long, or even an inch long to work just fine, if its threads are cut correcly, and the back of the barrel is threaded correctly. Many of the old guns had barely 1/2" of plug in the barrel. But they work fine.
Seems to me that if you build a pistol without considering where the pan is going to locate in relation to the front of your breechplug, and before you created the breechplug and thread the barrel, you have the cart and the horse turned around. NO?
What you are suggesting is a builder having to jump through hoops to correct a fundamental flaw in the construction of the gun. At the current cost of pistol barrels, and breechplugs, I would rather buy a new barrel and start over, and build it correctly, than to compromise the threads of the breechplug, or have to locate a liner someplace other than an optimum location.
I have owned a rifle that had a groove filed into the face of the breechplug to allot access to the vent. The gun shot, but that grooved gathered crud fast, and I was always having to clean it with a wire after 5-10 shots, depending on the humidity. I wish the builder had taken the time FIRST, to locate the front of the plug, in relation to where he was going to place the pan, and touch hole, so that there was a small space- say 1/8"- between the breechplug face, and my vent.