I'll answer in order here...
jglsprings said:
Are the frame dimensions of your model 66 just that much bigger to allow no cut on the forcing cone or are they the same as your Model 19?
Or, do you think new design is a result of the two piece barrel assembly?
On another forum they were discussing the two piece barrel assembly as a better solution for the L frame Model 69 44 mag pistol that was just introduced.
Keep in mind that I measured the frame differences back in 2004 so I don't have the exact dimensional differences. IIRC (and I can try to confirm this numerically, later, if people want the info) the topstrap is slightly thicker, the frame is slightly longer from frame barrel opening to the rear sight too.
The re-design had to be done to allow the 2-piece barrel and frame-mounted firing pin. If you examine the parts, the barrel shroud has locating lugs that fit into recesses in the frame (from photos I've seen of a disassembled 620).
Is the 2-piece "better"? The new 66-7 shoots as accurately as any other snubby K-frame I've owned (10, 15, 19) and should perhaps do even better in a longer barrel because a tensioned barrel should not have any induced harmonics.
gav1230 said:
Besides the lock, is there any functional difference between the new and old ones? Most of the changes like MIM parts seem more like minor aesthetic differences.
Define "functional differences"... they operate the same as the old models. The firing pin was moved to be frame mounted. My old K-Frame HKS and Safariland speedloaders still work fine. Internally they've probably made some changes but I've not removed the sideplate to see.
Tom Servo said:
Bill, are you saying your 66 does not have the flat spot at the bottom of the forcing cone?
Absolutely correct.
Because the barrel tube screws into the frame opening and it's thinner than the 1-piece barrel, there is more room on the frame below the forcing cone area.
Deaf Smith said:
The changes are made to make it cost less but the price will be higher.
If you speak of manufacturing costs will be less, that's probably true. There is constant pressure to reduce the cost of good and cost of manufacturing to remain competitive and affordable. The use of MIM parts is not new, nor is it detrimental -- Colt used an early version by using sintered powdered metal parts in the Trooper Mk III and later the King Cobra. Countersunk chambers were found to be unnecessary with the reliability of modern ammunition.
The barrel change addresses a weakness in the original K-Frame design (which was designed for a 17,000 psi .38 Special) when it was made to fire the .357 magnum. The frame changes incorporate modifications for a frame-mounted firing pin (which reduces chances of breaking the "hammer nose" used on older S&W's) and locator recesses for the barrel shroud. The topstrap was beefed up a little too.
None of those changes are free. I have no idea how many engineering man-hours were devoted to the redesign, prototyping and testing, much less internal documentation, drawings, specification, etc. ad nauseum.