The lower the bullet weight, the faster velocity it can be pushed. This is true for any caliber of gun. The most pressure is generated in the chamber and hits the forcing cone pretty hard on magnum loads.
The bottom of the forcing cone on a K frame has a flat milled on it to clear the top of the crane. That makes a thinner place on the barrel than the rest of it, so it's the first place to crack when it is over stressed.
I have seen a lot of K frame forcing cones cracked from shooting hot loads or just a lot of target loads. I had a M19 (before there were L frames) that was my only match gun for 3 years. I put around 30,000 rounds of wadcutters and a couple thousand rounds of magnums through it a year. It never did crack. I've had PPC guns that the barrel cracked after only a few tens of thousands of wadcutters. Once the forcing cone cracks, all you can do is replace the barrel. It won't shoot groups any more. Sometimes it binds up the opening and closing of the cylinder.
I have come to the conclusion that there is no way to predict if a barrel will crack, some do, some don't. I have long since switched over to L and N frames for competition. They never have that problem.
|