I have an SW99 in 40 S&W and have been thinking about a 357 Sig conversion. It has been said that the 9mm barrel flares out a bit at the end to take up the same space as the 40 S&W barrel so the two can use the same basic slide. I'd like to confirm that before spending the money on a 9mm barrel to ream. The measurements from my barrel are:

OD at the muzzle is 0.585"
Total length is 4.145"

If someone could measure a 9mm barrel, I'd really appreciate it. I know there were far fewer 9mm SW99s than 40s, but I figure it's worth asking. If nobody can confirm or deny the measurements, I'll probably take the risk and order one anyway.

Thanks!

I don't know why I bother trying to help people.

The P99s use very different slides with more material at the muzzle end of the 40 to increase total slide mass, but that isn't the case with the SW99. The P99 9mm barrels are also have a smaller OD than the P99 40 barrels. With the SW99, unless the 40 is slightly longer or something that's hard to tell without having them side by side, the slide profiles between the two calibers are the same. The real question is whether the hole in the end of the slide is the same too. If it is, reaming and swapping in a 9mm barrel should be all that's necessary. I've rechambered barrels before.

Wow. If I offended you, I'm sorry. You stated that the two slides were different near the muzzle, maybe they are, I just haven't seen it; they aren't different the same way the P99 slides are different as far as I can tell. If you know differently, please speak up, I'm here looking for information to keep my from chasing my tail if somone knows that it won't work. I just registered on here today, I usually hang out on the Walther forums for information about this gun as I have a P99 9mm as well.

Oh well, I didn't really expect anyone to have one, but I thought I'd give it a shot. I'll probably order the barrel tomorrow and let everyone know how it compares when I get it. It's a special order kind of item, so it could be a while.

To be continued...

Well, I had ordered from Midway, but I was just notified that the barrel has been discontinued by S&W and they can't get it. I'm going to contact S&W directly, but if anyone has a lead on one of these barrels, please let me know.

Ok guy's I am new gunsmith and have some questions about the S&W SW99 are the parts interchangeable with the Walther P-99 mine is a 9mm found in a local pawn shop I paid less then 150.00 as the owner is a friend. I need to replace the barrel will the 9mm Walther P-99 barrel fit and work in the S&W 99? Any guidence from a Senior Armorer or Gunsmith will be a blessing my name is Mark I can be reached at mda [email protected] thank you very kindly