Purchased one recently (threaded). Fits in the slide. The dimensions appear identical to the naked eye. On assembly, the frame snags on something which I believe could be the lugs. My Bar-Sto 9mm conversion barrel did not need fitting. I can't seem to figure this out. Appreciate any feedback. Thanks.

The OEM barrel is not designed to fit and work in a .40 slide. If you measured with a caliper, you would find some differences. If you shot the pistol this way, something would be damaged.

It works, I posted here about this several years ago and many others have tried it . The 9mm barrel works well in the P239/40. You can even use your 40 magazines, or buy some 357 SIG mags. In my experience, don't even worry about the slight difference in point of impact.

If you do a search here, there have been MANY threads on this.

Well,. That's two WILDLY divergent opinions.
Experts? What say you?

I read the posts from before. It works for the people that posted. I won't know if it actually works for my 239 since I could not assemble the slide to the frame. There is a snag that I could not see. I tried sliding frame to slide with just the barrel and the snag is still there. I do not want to force it and break it. I wonder if its worth the time and effort to have a gunsmith troubleshoot it. Any advice? Thanks.

factory barrels bought as spare parts are not 100% drop-in. Again, if you do a search there are numerous posts on barrels that do not fit. Chances are yours is contacting the locking insert. The barrel may not be fully seating into the slide, or the bottom of the feed ramp needs to be stoned down.

Here is just one:
https://sigforum.com/eve/forums...0601935/m/7970073854

Thanks for the link GaryBF. I will give it a go.

barrel fitment is a real thing. Most don't need it but some do. If you want it to run then have someone look at it, if you are not comfortable with a little metal removal...

I used a Sig 9mm barrel in my P239 that was originally purchased in .357 Sig. The 9mm barrel isn't just reliable, it's the most accurate set up I have with this pistol (that also includes a .40 S&W barrel).