I took the 640-1 pro out to the range yesterday with the following results:
1) 100% ignition of factory primers and ammunition including Corbon, Speer, Buffalo Bore, & Underwood
2) Vastly improved and centered primer strikes
3) High accuracy
4) Mechanical integrity, including no thumb piece, cylinder locking, or action related issues
As a result, this S&W has once again returned to trusted status and is part of the carry rotation. I do not blame the ammo for previous issues. It is just one of those times when a firearm needs a little bit of extra love from the factory. I am pleased with the S&W service team and with this firearm.
Got it loaded up with BUFFALO-BARNES LEAD-FREE Tactical 357 Mag Low Flash-Short Barrel - 125 gr. Barnes XPB @ 1225 fps (from 2.5"), which is, in my opinion, superior to Corbon's DPX load of the same bullet; and Underwoods 158 grain Gold Dot .357 Magnum ( Muzzle Velocity: 1475 fps out of a 4" barrel), which is mighty.
Now I just have to wait for some grips from Jim Badger to arrive, and I'm all set for 2012.