Hey, I just had that happen to one of my vintage .22 Mags, two weeks ago. I was shooting it and a core separated from the jacket and the jacket remained in the barrel. Next shot bugled the barrel. I cut it off and re-crowned the barrel, but it was right at 16" and too short for a .22 mag. So, I contacted the ammo manufacturer, great costmer service. Told me to rebarrel the gun and send receipts for barrel and gunsmith work and they would re-imburse me. My gunsmith and I removed the old barrel today, had a heck of a time getting the barrel off, screwed on with 24 TPI. Green Mountain Barrels shipped to me today, a .22" tapered, blued and fluted barrel for a Ruger 77/22. When it arrives, we'll turn off the end and thread it for my gun.