I have the new 66-8, 4.25 barrel. I just picked it up.

I haven't gotten it to the range yet, but from all I've read, this new combat magnum is much improved. The main weak point of the old K-frame was the relief cut at the 6 o clock position of the forcing cone. It was fine with .38, and was okay with .158 grain magnums, but if you went with the 125 gr. magnums, the cones would crack. There was also complaints about endshake and frame stretch.

The new metallurgy in the new guns are great. The forcing cone on the new K-frame magnum is full thickness all around. While the lighter weight of the frame will induce more endshake than an L-frame, I think it's about as durable as you can make a small/medium frame magnum.

Keep the 125 gr. magnums to reasonable levels. I've seen the mighty GP100's with eroded forcing cones from a lot of the 125 gr. stuff.

The only 'concern' I have with the new K-frame magnum is the deletion of the gas ring. This allows carbon and lead fouling to accumulate more quickly in the yoke tube. If the specs are tight, the cylinder will get sluggish rotation.