An hour? That's good compared to some barrels. My old DCM Garand took four or five hours to clean using Sweets 7.62 (stronger ammonia cleaner than Butches), plus and overnight soak. Accuracy would begin to deteriorate seriously at 40 rounds. I consider that deterioration a good indicator of serious fouling build-up. Some barrels can foul that badly in just 20 rounds.
I should add that with break-in, I also usually precede and follow the use of abrasive cleaner with a couple of patches of a copper removing cleaner that turns color, so I can get an indication of whether or not any copper is still there? Currently, I like Boretech Eliminator for that as it turns blue as fast as you can push it through a bore. It has no ammonia in it at all. I have to use a plastic jag with it as a brass jag makes it blue before it can get down the barrel. Another board member recommended the nickel-plated jags sold by Midway for that purpose. In each case the first patch just gets grime out of the way, while the second serves as the clear color indicator. This proves that the abrasive cleaner has done its job. I used to use Butches Bore Shine, and Shooter's Choice before Butches and Sweets when Shooter's Choice didn't seem up to it. KG12 may be the best copper cleaner, but it doesn't turn blue or green. Wipe-out has an optional accelerator that may achieve the same thing, but that's too much trouble to haul two solutions to the range. All the chemical cleaners take time to act. Same with an electrolytic cleaner like the Foul Out. They work well, but at the range you usually want to get it over with in few minutes, so the abrasive polishing cleaners make the most sense for getting the job done there so you can shoot again.
The way I use the abrasive cleaners is to take an undersize bore brush (like a .270 brush for the .308 bores) and wrap two patches around them, then smear the outer patch with the abrasive compound. Ever since Merrill Martin published that he could see even bronze brush marks in bores, I have used Hoppe's Nylon brushes for this. I push the abrasive loaded cleaning patch into the gun and work it back and forth. Anymore, I will usually use a few short strokes near the chamber at the beginning, since the most copper fouling usually builds up in the first couple of inches inf front of the throat. I then expand the strokes into the rest of the bore.
By way of "measurement", when I firelapped the bore of that old Garand (about 16 years ago) I was then using the NECO kit and jacketed bullets pulled from M2 ball. Those bullets have a crimp indentation in their middle so they only contact the bore in a couple of rings fore and aft of the center of the bearing surface. That thin contact area fills the grooves quite well, unlike a long bullet bearing surface which tends to fail to fill the bottom corners of the lands at low pressure. 8 grains of Unique was the charge. The NECO system has you shoot 5 then clean and slug the bore to check progress.
I did the cleaning with the patched brush and Iosso Bore Cleaner, which is a white mild abrasive paste. Since the Garand cannot be cleaned from the breech end, I used a muzzle bore guide, inserted the cleaning rod and until the brush protruded at the breech, then wrapped the patches and smeared the cleaning paste onto it by turning the rod. The first cleaning after the first five firelapping shots consisted of two patches of Shooter's Choice, the first to remove carbon, and the second as a color indicator to see if there was copper there? I ran one patched brush and Iosso paste for 20 strokes and put two more Shooter's Choice patches through, the first to clean the paste out and the second to check the color. Still green. 20 more strokes with new patches and paste on the brush. Two more Shooter's Choice patches. Still green. 20 more strokes with new patches and paste on the brush. Two more Shooter's Choice patches. Finally, no green. All that just for five very low pressure shots.
As the firelapping progressed, the Shooter's Choice revealed less and less green. By the time I got near the end of the process, I was running just one patched brush through and seeing no copper signs on the follow-up Shooter's Choice patches. So, after the final five polishing shots, I ran just one set of patches only 10 strokes and found it had completely removed any sign of the copper. That's why I say firelapping made the bore roughly six times easier to clean. It's not a precise measurement, but provides a feel for the process's effect.
When you do the break-in, you may want to add the color indicating patches? If you don't get all the copper out between shots, you have not laid bare the rough spots for the next shot to help burnish down.
