I am currently working on my fourth conversion, a .450 #2 NE. I use the thread and solder method because I believe that it is inherently stronger than threading alone. The threads, of necessity, must have some clearance between the male and female threads, in order for them to function. A good medium temperature solder, I use Hi-Force from Brownells, will fill all of these voids left by the machining process and I believe results in a stronger, more homogeneous assembly. I "pre-tin" both the barrel shank and the mono-block, using the recommended flux, then wash everything thouroughly with hot water and soap, to remove the acid, before final assembly. Without pre-tinning, it is virtually impossible to get the solder to flow by capillary action and achieve 100% coverage. The heat required, will cause too much oxidation of the steel, long before you achieve that coverage.