The problem was related to hollow base bullets with too thin a skirt, and trying to drive it too fast. Skirt would separate and stay in the barrel, next round would result in severe over pressure and the barrel would bulge or split because hammerli turned the main length of the barrel too thin. Their intention was to reduce forward weight on a six inch barrel. Most of these happened in Australia where thin skirts, max loads, and high summer heat led to failures. Mine had a split barrel when I bought it, had been welded and straightened by a master smith, so inspite of looking like the devil had a dance party in it, it still shoots very well. But I am still trying to find a replacement.
Dr Jim