Yeah, the 125 grain mags are the worst offenders. The .357 was born from a K frame .38 Before then, cops who wanted a .357 carried a big N frame. So Bill Jordan designs the K frame model 19 with S&W. They took a K frame .38, slightly lengthed the cylinder to accomodate .357 rounds, and used a different heat treating to withstand the higher pressure .357. Jordan used to refer to it as a ".38 that can shoot .357 for business". The forcing cone on a K frame .357 has a flat spot on the six o'clock position to allow the cylinder to close. That's the weak spot on them and where the forcing cone will crack. PD's used to qualify with .38 and carry 158 grain .357 for duty. Time went on and lawsuits came about that mandated cops qualify with what they carry. That was also around the same time the 158 grain went out of style in favor of the 125 grain .357. That's when problems began. some guys have shot nothing but .357 through their guns and they have held up. others have cracked forcing cones relatively early. The lighter bullets are faster moving and are more liable to cause problems. So if you are gonna shoot magnums, stick with 158, and don't shoot them exclusively. Gun might be Ok with them all the time, but if you crack the cone, you're out of luck. The gun was designed around a 158 grain round anyway.
I know I would not hesitate to shoot whatver .357 I wanted through my Service Six. My S&W 13 gets maybe 18 rounds a year of .357, and then only 158 grain. Also, modern 125 or 110 ammo isn't as hot as it was in the 70's, so maybe the problem isn't as big a deal anymore, but I wouldn't chance it. Finally, keep the gun clean, ESPECIALLY the forcing cone. Many believe it was the combo of a dirty forcing cone and the lighter rounds that cracked them. If you don't already have one, every revolver owner NEEDS a Lewis Lead Remover. Brownells sells them exclusively. They get ALL the lead out with one pass, and have a special forcing cone attachment to really get that clean, too.
Last edited by Homerboy; December 4, 2012 at 10:46 AM.