I have a W.German Sig P226 in 9mm.  I want to carry this for duty use in 40S&W.  My question is does anyone know if it is possible to replace the oldschool stamped slide with a new machined stainless one so I can make the caliber switch?  Thanks

Basically this should pose no real problem IMHO as you're swapping slides. As far as I recall the sizes of both slides are similar only big difference is in the barrel area (.40S&W has a wider breech - because of the higher pressures).
But I'm gonna give my contact at J.P. Sauer & Sohn (Eckernforde Germany) a call to be 100% sure and update this reply when I have a final answer.

Update:
Just been on the phone with Sauer company and basically there's no problem in swapping out entire slides. Yet they suggest to go through a certified SIGsmith to get a propper slide-to-frame fit.

Edited because of the above update.

C-2-6

Is the mag profile different for the .40 than the 9mm though?  I know the mag profile, and consequently the mag well shape itself, is different between the 9mm and .40 P229.  The .40 and 9mm mags are not the same mag.  I would assume that the mags would be of similar type for the P226, just longer.  I'd check into this a bit more.

The cost of the parts may be of concern as well.  It may be better economically to just sell the 9mm and get a new whole .40.  

Ross

Quoted: Is the mag profile different for the .40 than the 9mm though? ... I would assume that the mags would be of similar type for the P226, just longer.

For the P226 there are no differences between 9mm and 40S&W mags profilewize. They are both of the same size/width and are fully interchangeable. You might even get a 30rd "9mm" mag and top it off with 40S&W for some added firepower (if you were legally allowed to).
I think you got it mixed up with the P229. In that case the 40S&W/375SIG mags are a bit wider in the lower part of the magbody so they can't be used in a 9mm P229. The opposite is possible: 9mm P229 mags will fit a 40/375 P229.

Just my 2 Eurocents

C-2-6

Yup, you're right.  I was thinking P229.  At one time I had a P229 in .40 and in 9mm.  They were two very different guns.  You couldn't even swap slides on them.  

Ross

That may not be a great idea depending on when your SiG 226 was made. The 226 frame was never designed for the 40S&W or the 357SiG and they had some slide failures with the earliest mods. I think that Chris has some info on when they beefed up the 226 slides on his FAQ.

My P226 is stamped "Made in W. Germany" so I think it is one of the older ones.  Maybe you are right about the weak frame.  I will look into buying a new one.  Good excuse to get another Sig!  

Thanks everyone for your input.