The "why's" in discussions like these are always interesting and informing. From personal experience, overheard from someone who claims personal experience, overheard from someone who does not have personal experience, just a logical and reasonable guess...
Most would probably agree that barrel burner's, overboar cartridges are age old arguments that will always not be agreed on by everyone. This is not meant to be yet another argument about them at all, rather just some observations from personal experience and those of personal friends that most likely will just add to the confusion of others (like it has for me sometimes).
Despite cartridges being commonly labeled as BB/OB, they can and have stayed true in firearms for decades for some folks. Why? I've heard/read some of the suggested reasons attributed to why, but that doesn't necessarily make them fact and maybe just reasonable assumptions. But it is fact that real life experiences have varied with the same cartridges commonly called BB/OB.
Lot's of folks on-line say they have burned out 243Win barrels, yet I know a few folks personally who have been using their same old factory stock 243Win's all their life for deer, predator and varmint hunting and they are still very capable for all the hunting they do with them. And with the same scrawny factory sporter barrel that came on them new. No idea of round counts on any of them, although I know one gent shoots many hundreds if not thousands in his every year as a serious P&V hunter plus for big game. Surely those that have been used regular for up to 4-5 decades for P&V hunting have shot way more rounds than some say have burned out 243Win barrels. They all reload, but I seriously doubt any of them shoot reduced loads simply because of the ranges they are commonly shot at for varmints alone (especially rock chucks/prairie dogs). That one gent has shot deer with his further than many would even try to shoot varmints or predators with it.
Personally I've had some typically called BB/OB (22 Varminter, 220 Swift, lots of wildcats) that I used for P&V hunting for decades and had to have shot countless thousands of rounds through each without shooting out their barrels. I too was a reloader from the late 50's on, and did not shoot reduced loads in them.
So in my case anyway, so called BB/OB's and not discounted simply because of that moniker. Of those the OP started this thread with, I only have a WSSM (243). I bought it for a specific purpose that I am still confident it would excel for... but unfortunately my health failed before I got to ever shoot it to find out, so it remains NIB unfired. So I actually have no personal experience with any of those being discussed here in particular.
Will the SAUM, WSM, WSSM cartridges survive? I have no idea with varied attitudes about BB/OB.
Was there even a need for them? Certainly, just because something doesn't float your boat it can certainly float somebody else's. That 243WSSM I bought wasn't really needed, I had lots of other firearms that could have done the job I bought it for... but I thought it would do it more efficiently than any of them. Besides, any excuse to buy another firearm with all it's gear for a new cartirdge to play with was enough. I was running out of wildcats I wanted to try and hadn't yet.
