Bob Bell, the longtime gunwriter and scope guy for GUN DIGEST for decades, fired 12,000 rounds through a SAKO .222. I'd have to look up the details, but I believe all cartridges were loaded with war surplus 4895 powder. When he noticed the accuracy deterioration, Bell had the barrel set back and rechambered to .223. It never did shoot as well as it had in .222, so the barrel was probably truly worn out.
