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Message: <blockquote data-quote="_CY_" data-source="post: 1273419" data-attributes="member: 7629">for the longest time mistakenly thought the 120 grain warnings on my 340PD barrel was for lighter bullets un-seating. and that it was ok to use heavier bullets in all .357 loads. after several conversations with S&W customer service reps. they informed me 120 gr warnings was only for revolvers with Ti cylinders. lighter bullets use slower burning powders, so bullet will have left barrel before powder has fully burned. this would increase erosion of Titanium cylinders. what alerted me to differences was M&P 340, only one oz heavier than my 340PD. yet carried no 120 gr warning. M&P 340 has a steel cylinder and are not effected by slow burning powders. evidently testing for bullets unseating applies to ALL light weight revolvers shooting magnum loads. it's easy to see where one could be confused at the two very different warnings. sometimes both applying to the same revolver.</blockquote>