762 ULTRAMAGA
WKR
It's not unburnt powder it's carbon fouling, every can will fill up with gunk if not cleaned regardless of barrel length. Bigger powder charges will require more frequent cleaning whether its on a 16 or 26" barrelI'd keep an eye, especially with a RUM with unburnt powder building up in the can. I have a buddy who's can exploded due to powder build up, and another who was burnt the crown off his barrel on a 300 PRC, both were either 18 or 20" pipes pushing big pills with slow burning powder.