Just installed a threaded SS 9mm Storm lake in my XD 40 service. Only problem, if it is a problem. The barrel is just a little loose. It sticks out past the slide about 3/4 of an inch. I can push it up or side-to-side about 1/32 of an inch. My 357sig aftermarket brl. And the factory Springfield 40 S&W brl. does not move hardly at all. I called and talked to a tech person at SL and they said that much movement was within tolerance. Haven't shot it yet might be fine.

I have the same set up with an early Service model and the 9mm barrel out shoots the 40 S&W barrel by a considerable margin. The only " negative" is that some brands of factory ammo do not push the slide back far enough to engage the slide stop after the last round. This is particularly true if a new recoil spring is being used. It becomes a little less noticeable after a couple thousand rounds but it will still happen. Remington/UMC seems to be the most frequent culprit but it has happened with Fiocchi, Winchester, Federal, CCI, S&B, and probably a couple other lower cost lines of ammo.

I have not had the same happen with a conversion barrel in an M&P yet but I have less than 100 rounds through it so far and have not gone through a number of brands. It is also getting close to spring replacement so I would not be surprised if a failure to lock the slide back occurs with a new spring.

Thanks for the great information. Mostly with my other 9mm's I use blazer brass ammo. Might get a chance to shoot it tommorow. I bought three new 9mm springfield mags and ordered 3-round mag extensions. Hope all goes good.
Thanks again Erich