Estand wrote:I am no expert, but this is shared and established info I obtained from more than one of the large S&W forums and the same subject continues to be active. And I understand not needing a match barrel, neither did I. But you DO need a conversion barrel. If you had oem 9mm barrel you would see the outer dimensions are smaller than the 40. It will be "loose" in your 40 and lock up will be less than good. People have done it with partial success, but it is reported to be unsafe and less accurate. That is what the conversion barrels are made for. It's basically a 40s&w barrel, with a 9mm chamber and bore. I encourage you to visit one of the S&W forums first. And I don't know what is different about the shield that makes this a non issue.
The only thing that could be different is if S&W made the shield OEM barrels the same OD in order to use more of the same parts between the two calibers. I doubt this is the case. I have seen OEM 9mm Glock barrels used in .40 Glocks but it is very loose and I would not trust it.