In MOST cases the sabot will blow before the barrel and then needs to be cleaned/inspected for safety reasons. The barrel is rated at well over 100k PSI BURST strength. That doesn't mean it wont bulge on a double charge (as an example) It might. William Ball (co-inventor) proved this years ago by shooting a double charge without the barrel failing.

Let me know if you want some links to the load data ive mentioned. Most of it will include pressure traces and fps. There is a HUGE data base on Doug's from VERY well respected members.