when did S&W install the internal sliding block to keep the cylinder bolt from moving when the trigger is pulled. I assume it is to keep the cylinder from unlatching under recoil

__________________
age is just a number

According to the Standard Catalog IV, the bolt block was added in 1989 with the 629-3 revision.

__________________
Don't You Ever Wash That Thing

thank you for the answer.

__________________
age is just a number

The referred to it as the “endurance package”

What is the difference between a 29/629-3 and a 29/629-4? They both have the "endurance package" and I do not see the difference when looking. Thank you.

The engineering changes that earned the 29-2 its dashes were incorporated into the first variation of the 629, the no dash, so while the two models were being made concurrently 29 dash numbers were two higher than 629 dash numbers. For example, the change to the 629-1 and 29-3 was elimination of recessed chambers and the barrel pin. The first endurance package features were introduced during 629-2 production creating the 629-2E. The 629-3 had the full endurance package. Most 629-3s had the older rear sights that were square at the front end and were not drilled and tapped for mounting optics. In 629-3s only the full lug Classic model had a rear sight that was rounded on its front end with threaded holes for scope mounting under it. The 629-3 Classic's rear sight had different dimensions than the currently used one that was introduced with the 629-4. All 629-4s had the currently used rear sight with threaded holes for scope mounting under it. Although dash numbers were not increased only for rounding the butt frame, in 629-3s only the Classic line was round butt. During 629-4 production S&W discontinued all square butt revolver frames. They eventually made more square butt revolvers but for years it was round butts only.

I hope that answers your question.

Thank you for the quick reply. I asked because I am trying to find a 29,4"bbl.,blue and I could not remember the best # to buy. I want one in new/ like new condition and they are difficult to find.