Jeff, thanks for asking, here is my PM response to your question:
Welcome to the forum. Another favorite that you might like is http://singleactions.proboards.com/ and you will find a good deal of helpful sorts and information there. I am a graduate of the Colorado School of Trades Gunsmithing school and when all our better sixgunsmiths started getting backlogged so badly and charging so much (75-100 per hour) I decided I better lend a hand. If a .451" bullet stops in the throat, that is an indicator that the throat is undersize. BUT, a couple of important things to remember are you cannot go by what the box says the bullet size is, nor can you trust what the dial caliper says because neither is accurate enough for our purposes here. You must measure the slugs with a micrometer and the throats are best measured with pin gauges. So let's do this. Send me both cylinders. Let me first get some accurate measurements on them. Include some of the bullets you want to shoot. This is important because if I cut your throats to shoot a .453" diameter cast bullet and you shoot a .452" cast bullet, the propellant gas can blow past the bullet while it is in the throat. This will force the bullet lubricant to vacate the bullet grease groove while in the throat/forcing cone intersection and your bullet will enter the barrel with not enough lubricant. This causes friction which leads to leading and poor accuracy. What you want instead is a bullet that will "seal" your throats during this process. This would indicate a cast bullet no smaller than .453". So, what should happen is the propellant gasses can not over take the bullet from the rear, the front will begin to "accordian" or collapse as it engages the rifling and the lubricant with no where else to go will be forced to create a "liquid gasket" between the bullet lead and the barrel steel all the way down the barrel.
So, the first thing we need to do is measure and find out what we are looking at. We will only correct the throats if need be. I need all your contact information as I do not do any work until I measure everything and give you my best price quote. It is important to remember, getting the cylinder throats right is only the FIRST step. You may still have poor accuracy for barrel restriction or poor barrel/chamber alignment.
Some guys don't need their throats corrected. They just need to shoot the correct diameter bullet for their throats. Some guys have throats very badly undersized and those throats can be a trial. Others are very minor to get right. We just don't know until we see. Last, let's not spend the money to do the 45 Auto Rim modification until we get it shooting right as a ACP cylinder. No sense in cutting it for AR only to find out it doesn't align properly with the barrel.
So, as you can see, what we want to do is go at this step by step eliminating potential problems along the way as we come to them. That is, we correct the sixgun from the throats to the muzzle. Here is a link to an article I wrote in 2011 trying to help guys understand how this all works. http://singleactions.proboards.com/
Last, I provide you with all my contact information because I am not going to cut your throats and then abandon you. Correcting the throats is just the FIRST step. I will be there to help you even if you choose to not hire me. Be sure to provide me with your information as sometimes it is easier to call instead of typing a book and I tend to often be hands busy. So there you go. We are on the way, but be sure you CLEAN them cylinders before you send them! Saves you money!!! LOL,
best,
fermin
