Jack V wrote:More to the point the reason they say hand lapping is because a machine can't feel . Hand lapping is done by feel not actual measurements . Having said that I do believe that some barrel makers do in fact do some machine lapping and then finish up by hand.
The lapping is only to smooth it up and remove burrs not change the basic bore dimensions . During the process you can get a feel for how good the bore is , how straight it is and which end should be the muzzle .
Directly from the Lilja barrels website, note the hi lighted section
Chronos
A. The hand lapping process, that all of our barrels undergo, ensures that you will receive a rifle barrel that has the very best and most desirable type of internal finish that we can provide.
The lapping operation brings the final internal dimensions up to size and also improves the finish. No production barrels are hand lapped, only the finest custom barrels receive this very important operation. And it is partly for this reason that hand lapped barrels cost more than lower grade production barrels.
In practice, a lap is cast around a rod placed inside the barrel. The profile of the rifling is cast into the lap ensuring a very precise fit with that individual barrel. The lap is then "charged" with lapping compound, oiled, and pushed and pulled repeatedly through the length of the barrel. The lap is "recharged" and oiled many times and several new laps will be cast before the lapping procedure is completed. The man doing the lapping judges when the barrel is finished by a very experienced feel for the job, inspecting the internal finish as it develops with a full length borescope, and by measuring the diameters of the lands and grooves.
We have, over the years, developed a process that we feel gives us the very best finish and uniformity of diameters the full length of the barrel, that we can obtain. And the proof is, in our opinion, in the very minimal amount of bullet jacket fouling that our barrels produce, and in their outstanding accuracy.
Our process completely eliminates all tooling marks from the inside of the barrel. And very importantly the resulting finish runs parallel with the rifling.
It is for these reasons that we discourage anyone from submitting their new Lilja rifle barrel to any subsequent internal finishing operation.