Are you talking the bullet or the coating that's hard?Erosion or perhaps more aptly called "wear"does happen from hard bullets going thru the bbl, right? Since powder coated boolits in my experience are "harder than the hubs of hell ", I would think that shooting them would cause more wear on a bbl than softer cast bullets.
Okay, but the ductile, "soft" bullet is underneath and the coating will give with the bullet as it enters the leade. It's not like it's steel on steel. I would be concerned if the coating had a Bhn of 50 or something, but I've never heard that it does, maybe one of the PC boys here can offer some info. I was also concerned the powder coat might be abrasive, but I've seen no reports of that either. The paper used in paper patching has some abrasive quality, some types at least, but users report a polishing action. I have no experience with PCing at all, but considering that even with copper clad jacketed bullets we know it's the hot loads that cause the problems...I'm not sure it's a giant issue.Coating
On the Swift- IMO the barrel burning was at least partially due to people taking heavy rimfire barrels and trying to use them as Swift barrels back in the early days. And many barrels back then were a lot softer than what we use today. Shoulder angle, powders, etc. also probably had a lot to do with it. I have a 6.5-06 barrel that started life as a Swift barrel back in the late 40's and used by a dedicated chuck hunter. He "shot out" the Swift barrel and then "shot out" the 6.5 barrel. I'm betting it was the relatively soft steel and hot loads doing the dirty deed.I believe it was Townson that did the between wars study with some 10 03's to determine barrel accuracy life . The results were that the life was 30 seconds . At .007 seconds being the time between primer ignition and clearing the muzzle as barrel time it comes out at 10,000 rounds . The between wars early 06' was probably loaded with something less abusive than Cordite and faster than 4350 probably something akin to BL-C produced by DuPont no doubt maybe summer and winter ammo ..... In any case it was just standard issue FMJ ball probably surplus from the 1918 to 1919 production in about 1934/5 as I recall , it's been a long time and when wasn't as important as the context and outcome. We have in theory better suited steels , infinite powder choices , and really we should be getting longer barrel life not less . We have introduced powders that "scrub copper fouling" as they go , (in my best gump)"I ain't a smart man but" as a mechanic if it removes bearing transfer as it's laying down more it's going to decrease the net life expectancy . You just can't strip away something while you add to it . Applying a layer of antistick slickum' sure I'll buy that but I didn't see any difference in performance in several dry films that I tried , including a snake oil trial I tried over there most of 15 yr ago , dry film graphite, Teflon (which made a gooey mess and sucked in the cold as shotgun action slickum') and a couple.of.other wonder slide deals .
Old school 50kpsi 30 cal FMJ at 2/3 case dia to bore dia reaching maximum acceleration at 23" of barrel has a 10k round life for a GI barrel to hold 3 MOA .
Larger case to bore rates have faster wear . The kings of that example are the 220 Swift and 264 WM which is weird because something magical must happen in that .02 span between .264 and .284 because the 7mm RM has beat that wrap . The 22-250 is supposed to be hard on barrels but nothing like the Swift ....... The shoulder angle of the 22-250 maybe ? I mean if there were ever commercial brother of another mother's on the shelf those 2 are it . The 22-250 did have the advantage of more modern powders so maybe that's part of it , maybe a big part of it . I'd say that's probably the difference between the 264 and 7mm too .
Using the idea and scale the 25-06' should be a destroyer of barrels too but it was loaded with magnum type powders from the outset , and came in just in time for a war then got held up another 15-20 years and it had even better powders thanks to a million pounds of surplus H4831 left over from 20 mm cannon production .
Any time we load for zero deviation, maximum velocity, applications it's going to be hard on equipment.
When one leans on numbers to look for answers because that's a real standardized base to stand on BC is the only difference between nominal loadings by bullet weight between the 7RM and 06' . I don't know how life is with the 280 but with a little "headspace manipulation" the AI can get back the 100 fps it loses to the bore dia and the 06' . It's harder on barrels maybe than the RM which is weird because they are probably closer dimensionally than the 220 and 22-250 and share the shoulder but not the neck .
Just the mechanics point of view again but we are again entering a why some do and some don't situation that is driven by powder column length and the top 1/2" of the cases shape . Which sounds like an echo of something I read someplace now that I've written it down ....... Round , square , length , angle , taper , all applied to body , shoulder , and neck . It may have been during the Lazeroni push that I was reading about it all , years before the Short Mag run .
It can be bantered all day and night but until we have the means to look at the actual events that are occuring during .0095 seconds in something north of 100,000 fps maybe as high as 500k frames we can only tap the numbers and impact results.