RE: BP guns blowing up?
Many of the ruptures are avoidable. The 777 crud ring has caused alot of problems with short projectile seating. Pellets have caused problems after repeated breakage while loading. When breaking pellets repeatedly, they SLOWLY decrease bore wall strength where the powder sits. Swab often using 777... don't take chances... make sure the bullet is against the powder. When using pellets, it's SAFER not to use a grunting, tight-fitting bullet in combination with pellets.
If your sidelock suddenly starts pulling the hammer back to 1/2 cock.. somethings wrong that's creating back-pressure. If it gives you a burning spot on your hand, arm or face after firing, somethings wrong in the nipple thread area.
If the barrel becomes difficult to load (or) becomes too easy to load, there's a problem with it's iron/steel integrity. If blowback around the breechplug/209 primer area increases or the primer becomes distorted, frayed or mangled-looking, change that breechplug immediately. Also check the bottom holes in your nipples & breechplug for size variations & check the permanent seal & tightness on sidelock breechplugs.