It seems to me that there is a bit of a misunderstanding about what the chamber on a 1911 style pistol should be like. Over the past several years I have personally examined dozens of pistols with barrels that have been “professionally” installed by “competent” pistolsmiths. Without exception, all the barrels inspected had the same sort of issues. Below is a short evaluation of some of what I have seen and my opinion on the way a chamber should be done based both on personal experience and how I was taught.
First of all it seems that none of the smiths that installed barrels that I have seen realize the chamber that is cut in the barrel when you receive it from Kart, Bar-Sto, KKM, or whomever, is not finish reamed. With very few exceptions, most barrels, whether in a semi-custom gun from any number of makers to full house custom pistols from the most famous of smiths, have not had this most basic of steps completed.
Finish reaming the chamber is a simple action that can be accomplished by even a neophyte with a small bit of training and any number of manufacturers’ reamers. The two I recommend are Manson and Clymer. All that needs to be known is the depth of cut you desire from the back of the finished hood. On a .45acp, for example, it should be .905 to .908”, using good calibrated calipers, from the above mentioned hood area. Of course this is based on having a hood to breech face gap of just less than .001”. This will help make for good accuracy and reliability.
Perhaps most smiths don’t realize the chambers are not cut. It is very easy to tell if one has been done or not. For example, every Kart barrel I have fit has a bump in the chamber from the factory. It is apparently part of their barrel making process that leaves a slight raised area in the chamber. The bump is not a problem unless it is not removed. If left as is, I believe it can cause broken extractors, failures to feed and eject, not to mention accuracy suffers greatly.
Second, there has not been a single chamber I have examined that has been polished. Perhaps people actually believe that the lubricity traits of brass mean you don’t have to polish the corn cob rough chambers that come from most barrel makers. Or perhaps they think that after a couple thousand rounds the chamber will self polish. In either case they are, in my opinion, incorrect. I can totally understand a $500.00 bone stock pistol being this way, but a gun running from $1000.00 and up should be smooth and shiny in the chamber.
Finally, regarding 1911 barrel chambers is the throat area. Perhaps the second most misunderstood area of the barrel is the tiny ramp like space that leads the bullet into the chamber. Many people apparently fancy themselves as jewelers and feel the throat should be covered with as many facets as they can cut into such a tiny area with a dremel tool. Others seem to think the rougher it is the better it will function. Still others insist on over cutting it, rendering the barrel dangerous and useless, or making it so convex in shape that you couldn’t feed a round if your life depended on it, as well it may.
The reality of the throat area is that in my opinion and experience, for the best in reliable feeding, this area should be slightly concave, not convex, in shape. It should also have neither rough spots nor facets. This is not a diamond, it is a pistol barrel. Furthermore, along with the aforementioned chamber, it should be polished to a mirror finish. The top edge of it should be SLIGHTLY rolled over into the chamber for those reloaders who like the short bullets. And unlike some barrel makers believe, it should never be rounded under on the bottom edge where the barrel meets the frame, but rather sharp and smooth.
Of course I could go on and on about the nuances and minutia of barrel chambers, crowning, leg fit, hood gap, etc, but I don't want to bore you with all the details that fitting a barrel correctly entails as we would be here for days. I simply wanted to point out something that I see on a regular basis that could easily be corrected with a bit of care and instruction.