I was curious because i always see and hear people talking about the barrel swaps on glocks which makes them more appealing. I wonder if there are other makes that you can do that with?
Most of the people who swap barrels with the m&p usually get the conversion barrels which I believe is only made by storm lake at the moment(there may be others, but I don't remember at the moment). The issue you'd get from just buying a 9mm barrel and dropping it into a .40 is that there're are difference in the geometry of the outside dimensions which can effect lockup and timing and barrel/slide wear. Although I have heard of people doing that without issues, there's still a chance of damaging the m&p. I bought the storm lake conversion .40-9mm and still had some issues with the 9mm not sitting right and the firing pin missing the primer and hitting the rim. Not sure what caused it though, haven't used it since. I guess I need to try it out again and see. Those are just my oberservations and YMMV.
I was thinking that my extractor was the issue, I've got the 9mm mags, but as I said, the round wouldn't sit right and the firing pin would strike the rim or just outside the primer. I may get the APEX FRE and try it again. Plus it may help the occasional erratic ejecting of the shell casings...
I haven't tried swapping barrels yet...just bought my M&P 9 Pro this week. But if you look on Midways website, they have original S&W barrels for $68.00. They are sold out rite now...but the comments say they work great.