BoydAllen
Gold $$ Contributor
There are a couple of factors involved here. First of all, no matter how well lapped a barrel might be, when it is chambered there will be cross land machining marks on the angled part of the throat at the beginning of the lands. If the reamer has smoother edges it may not be as significant an issue, but to some extent it you will see an effect, which brings me to my second point. After the chamber is cut, some smiths do a little judicious polishing to smooth out the throat, while the barrel is still mounted in the lathe. A friend of mine is a smith who picked this up from one of the greats and he does it to all of the barrels that he chambers, very carefully. A couple of months ago I referred another friend to him for some barreling work, and he (the customer) was amazed as to how little color he saw when cleaning after the first shot. He was prepared to go through a 20 or 25 round procedure with several cleanings, but based on what he saw, there was little need. A well known competition shooter that I correspond with from time to time makes a habit of breaking in barrels with as light a load as possible, selecting a powder accordingly. High and normal pressure loads translate into more bullet side pressure, which he believes can complicate the break in process unnecessarily.