Although I use the ring-test here's another more visible means of testing. Just take a mouthful of cigar or pipe smoke, a straw or piece of thin neoprene tubing and blow the smoke into one of the vent holes on the underside of the barrel ribs. Smoke issuing from anywhere along the length of the ribs is a sure sign that you have a gap or solder failure. Just my 2c worth that works as nicely as my parafin wax chamber casts. Chops