After all the years i worked on doubles i noticed most blown bbls happen around the halfway point, just ahead of the forearm where pressure should have dropped by 60%. Most bbls mike out an average of .030 of an inch inwall thickness. The bores on most of these older double bbles. are tighter than todays standard. The old paper case was much thicker than plastic therefore the projectile (for lack of a better discription) was smaller in dia.than a plastic case with a shot cup that is bigger in dia. Couple that with increased pressure and older work hardened steel its no wonder we see these things happening. This is just my oppinion. Its always supprising to people who see a bbl. blown out almost flat, they cant believe how wide it is . Almost as wide as there eyes when it happens. I think if i had a high grade older double i would only use the older style European shells. Rich
