Originally Posted by stalkingbear
Do you own a borescope? Have you borescoped barrels before and after? In my 28 years of gumsmithing and competition shooting I have-a LOT. I.ve seen remarkable differences from hand lapping or breaking in the barrel..
Stalkingbear this thread has turned into the proverbial **** storm brother.
I, like stalkingbear, have also been a shooter and rifle builder for more years than some of you have been alive. As such we have much more personal contact with the people who actually make barrels for a living. Funny thing is I have never had one yet tell me that there is no benefit to barrel break in, and in fact have all recommended some form of break in. Tim North, to name and quote just one, of Broughton Barrels recommends at least a 5 round lead angle/throat break in. This is on a hand lapped barrel. Stalkingbear is also right when he says that a factory production bore will generally require more rounds to achieve desirable results.
Hand lapping is done a number of different ways and should NEVER be attempted by a home "gunsmith". I have hand lapped more bores than I can count over the years that I have been a riflesmith. In years past not all high quality bores were hand lapped as an integral part of the manufacturing process and was only offered as an option.
Some barrel makers lap to consistent bore, land, and groove dimensions, and others lap a taper to the bore. Both methods work admirably though I prefer a taped bore. Some use a cast slug and others use fiber tape with both mediums being impregnated with abrasive compound. A rod with a swivel handle, like a cleaning rod has, allows the slug to follow the rifling. Most will measure the bore during and after the process with inside calipers and/or lead slugs that can be formed to the bore, removed and then measured with a micrometer to verify dimensions. The finish of the bore after lapping will vary from barrel maker to barrel maker also. Too smooth a finish will increase the bearing surface area and create problems, and a rough finish will lead to faster copper fouling. Like the chamber finish, the finish should have no tooling flaws, but be rough enough to to reduce the bearing surface area.
We slug and borescope every bore we purchase and always will. If there are any flaws, which is very rare to non existent with the manufacturers we use, then the bore is rejected and replaced. Slugging the bore will tell us if the hole is round or egg shaped, whether the dimensions are consistent throughout the bore from one end to the other, and if the bore has a taper to it and how much taper. Boresoping will allow us to look for voids in the material or flaws that can be seen visually.