I have one of the new 66s with 2.75 barrrel. I own 15 other S&W revolvers of various models and age and the new 66's fit, finish and accuracy is as good or better than all of them. The lockup out of the box was very tight.

First time at the range I had a copper jacket shaving issue with 158 grain AE .357 semi jacketed ammunition. The buildup after three cylinders worth caused the revolver to lock up. I had shot 100 rounds of Remington 135 grain FMJ .38 spl prior to the .357s without issue.

The fouling was exactly like that which was reported by another owner in a previous post -- copper buildup at the top of the forcing cone. It was easy to remove after returning home from the range.

The following week I fired a mix of several types and weights of .38 and .357, including the 158 grain AE. 150 rounds total. The shaving did not occur again.

I have been to the range twice more and have had no further issues. It's almost as if the gun just needed to be loosened up a bit.