I'm FINALLY getting around to trying this out. I just got a tube in the mail. It's a 10" long A513 seamless tube with a .15" wall. It's just over .56 caliber. I figure I'll have enough length to fire 3 tightly wadded ball powder charges. The homemade pistol in the previous pic just doesn't have a long enough barrel for more than two.
"THE SIERRA JUST HOTEL TANGO FOXTROT -OVER"
MALO PERICULOSAM LIBERTATEM QUAM QUIETUM SERVITIUM