RedHawk44, Brian Pearce has researched the M696 in depth with S&W, and he believes the gun is capable of what he calls Category 3 loads (up to 25,000 psi). To quote him, "The factory conducted some rather strenuous torture tests, wherein the model 696 easily endured pressures well beyond anything we will present here."
A 250gr lead SWC at 950 fps does 95% of everything I need a handgun to do, and I can do this with selected powders at Pearce's "Category 1" pressure level of up to 15,500 psi (SAAMI max avg pressure for the .44 Special). My converted 681 is simply a 696 with a 4" inch barrel and fixed sights (which is exactly what I wanted). If (when?) the cylinder on my "691" blows or the forcing cone cracks, I'll be the first to let you know... :wink: