Originally Posted by stiab

I agree they appear to be, and was previously of the opinion that the .38 Special K frame and .357 K frame cylinders/frames were identical, or almost the same. At the time I was making an argument on another forum to shoot .38 Supers in .38 Special revolvers, and I used the 547 as an example of why it should be OK. That is when someone on that forum pointed out to me that the Model 547 was apparently made with the magnum qualifications.

I would like for someone who has actual knowledge to explain to me (us) what exactly is the difference between the frame/cylinder on a Model 64 and same era M66, that makes one magnum elgible and the other not (other than the length of the chamber). I assume the answer would include heat treatment. Anybody know for sure?