Just read an article (sorry I can't link to it right now) about a .20 caliber cartridge made by necking .223 brass, intended for AR platforms. All well and good if you like the idea...
Claimed ballistics were 40gr. bullet at 3900+fps. Again, that's fine if it's what you want but some years ago I followed several gunwriters' exploits with small-bore, mach 4 cartridges and it seemed like barrel life wasn't much due to the nature of the fouling under those conditions. Has anyone been able to solve that problem or was it just a matter of using better cleaning products?