memilanuk
Gold $$ Contributor
So... I was going to piggy back on the other thread here, but since its spiraled off in a different (non technical) direction, I decided to start a new thread of my own.
In the past, I've always just cleaned my barrels til the crud stopped coming out, and the patches stopped coming out blue. Seemed to work.
I bought a 'share' in a borescope at a local gunsmith shop years ago... basically I can go down there, put my barreled action in a jig, and look down it with a Hawkeye. Not too many surprises... some factory barrels that looked horrific but still shot fairly well, a Krieger medium Palma .30 cal barrel with 6k+ rounds was prettty well toast, etc. I always put my name in the hat at the BSWN to try and win the drawing for a new Hawkeye of my own, but no luck
Last year I decided a Lyman borescope would be worth the risk - maybe not the image quality of a Hawkeye, but good enough, and with image capture, for what I wanted.
Couple things I've 'seen' since then have surprised me a lot.
One, my normal routine of cleaning with WipeOut Accelerator + PatchOut til the black/blue stopped coming... was leaving an awful lot of both carbon and copper behind.
Two, the... for lack of a better term... 'burn pattern' or wear/erosion in the barrel looked a lot different than I expected.
Most of my past 'scoping with the Hawkeye had been on .30 cal barrels, shooting predominantly 155 gn bullets, with relatively short bearing surface, being propelled by either Varget or N150. The wear/erosion in those barrels (when cleaned down to more-or-less bare metal) showed some burning/checking erosion on the tops of the lands, some black crud in the corners of the grooves against the lands, and when that stuff was cleaned out, if it was a factory barrel, you could still see the tooling marks basically 'preserved' under the carbon. The center of the grooves was bright and shiny and looked like the main contact surface, as one would expect.
Most of the newer barrels have had a steady diet of 200 Hybrid (and more recently 200.20X) bullets propelled by Varget or H4895. I've looked at one with 2500+ rds thru it (toast), one with ~750 rds thru it, and one with ~200 rds thru it. Two different barrel makers. They all exhibit the same wear/erosion pattern. Little bit of wear on top of the lands, increasing with round count. Bright shiny strips in the corners of the grooves, no carbon trapped in there (good, I guess)... and the part that has me scratching my head... a big wide nasty looking strip of char right down the middle of *every* groove, starting a few inches ahead of the throat, and extending towards the muzzle. How long, and how deep, seems to correspond to the round count.
Basically, the way the barrels look to be eroding is almost the complete opposite of what I would expect, based on what I've seen in previous barrels shooting other (lighter) bullets. Somewhere around here I've got a barrel that had a steady diet of 185 Juggernauts and Varget; I'll have to see if I can find it and clean it up and see which way it looks.
I'm curious... anyone else with a bore scope seen similar burn/erosion with long/heavy bullets (for caliber) vs. short/light? Any ideas on why in the one case, the bottom of the grooves is shiny and polished (metal on metal) where in the other case its charred and burned away in the bottom of the groove before the lands?
In the past, I've always just cleaned my barrels til the crud stopped coming out, and the patches stopped coming out blue. Seemed to work.
I bought a 'share' in a borescope at a local gunsmith shop years ago... basically I can go down there, put my barreled action in a jig, and look down it with a Hawkeye. Not too many surprises... some factory barrels that looked horrific but still shot fairly well, a Krieger medium Palma .30 cal barrel with 6k+ rounds was prettty well toast, etc. I always put my name in the hat at the BSWN to try and win the drawing for a new Hawkeye of my own, but no luck

Last year I decided a Lyman borescope would be worth the risk - maybe not the image quality of a Hawkeye, but good enough, and with image capture, for what I wanted.
Couple things I've 'seen' since then have surprised me a lot.
One, my normal routine of cleaning with WipeOut Accelerator + PatchOut til the black/blue stopped coming... was leaving an awful lot of both carbon and copper behind.
Two, the... for lack of a better term... 'burn pattern' or wear/erosion in the barrel looked a lot different than I expected.
Most of my past 'scoping with the Hawkeye had been on .30 cal barrels, shooting predominantly 155 gn bullets, with relatively short bearing surface, being propelled by either Varget or N150. The wear/erosion in those barrels (when cleaned down to more-or-less bare metal) showed some burning/checking erosion on the tops of the lands, some black crud in the corners of the grooves against the lands, and when that stuff was cleaned out, if it was a factory barrel, you could still see the tooling marks basically 'preserved' under the carbon. The center of the grooves was bright and shiny and looked like the main contact surface, as one would expect.
Most of the newer barrels have had a steady diet of 200 Hybrid (and more recently 200.20X) bullets propelled by Varget or H4895. I've looked at one with 2500+ rds thru it (toast), one with ~750 rds thru it, and one with ~200 rds thru it. Two different barrel makers. They all exhibit the same wear/erosion pattern. Little bit of wear on top of the lands, increasing with round count. Bright shiny strips in the corners of the grooves, no carbon trapped in there (good, I guess)... and the part that has me scratching my head... a big wide nasty looking strip of char right down the middle of *every* groove, starting a few inches ahead of the throat, and extending towards the muzzle. How long, and how deep, seems to correspond to the round count.
Basically, the way the barrels look to be eroding is almost the complete opposite of what I would expect, based on what I've seen in previous barrels shooting other (lighter) bullets. Somewhere around here I've got a barrel that had a steady diet of 185 Juggernauts and Varget; I'll have to see if I can find it and clean it up and see which way it looks.
I'm curious... anyone else with a bore scope seen similar burn/erosion with long/heavy bullets (for caliber) vs. short/light? Any ideas on why in the one case, the bottom of the grooves is shiny and polished (metal on metal) where in the other case its charred and burned away in the bottom of the groove before the lands?