They work well for leading and copper fouling.
They don't sell well because they're expensive.
Never have figured out why someone would spend $1000+++ on a gun, and nit be welling to spend $75-$100 on a bore cleaner that doesn't require "scrubbing" that expenxive bore????
Oh, well. Every day I see $1500-$2000 rifles with $99 K-Mart scopes on them. Go figure!