I finally received the .40cal barrel and magazine from S&W today. Here is a pic comparing the 9mm and .40cal side by side and back to back so you can see how much the tangs differ in size.
So as it was mentioned in previous posts, you have to remove about .010 of an inch from each side of the tangs in order to make the .40cal barrel fit into the 9mm slide. I initially thought using a small hand file would work but when I tried it with mine, I found that I wasn't removing enough material to expose the bare mental even after filing for a few minutes straight. Maybe my files were just ****, who knows.
So then I took out the handy dandy Dremel and found these two grinding wheels that I would use. I don't know the actual names or textures but the red one was used to grind down most of the material and the gray one was used to clean up the grinds and smooth/polish the material.
So what I ended up doing was laying the Dremel down on the table, holding it with one hand then gently rubbing the barrel onto the wheel little by little. I started off grinding off enough to expose the bare metal on both sides, then measuring with my caliper tool, then grinding some more until I was close then finished it off with the gray grinding wheel to smooth out the grind.
At the end, this is what I ended up with:
I finished it off with some Birchwood Casey flat black marker and you can barely tell anything was done to it.
Here is a pick of the .40cal and 9mm barrels side by side after the .40cal was trimmed.
Here is a pic of the 9mm barrel on the slide before I put it back together.
Here is a pic of the .40cal barrel on the 9mm slide.
Side to side movement is exactly the same as the 9mm barrel; almost non-existent. The slide racking back and forth feels the same way as it does with the 9mm barrel and I cant feel or see any rubbing from the tangs on the slide. Measurements with the caliper are the same.
My next concern was with how the round seated on the slide once a round was chambered. I was curious as to how the bigger .40cal round would seat against the firing pin being that the diameter is a little larger then the 9mm round. So, using snap caps, I placed the rounds up against the slide under the extractor to see how they would fit.
9mm
.40cal
I reassembled the gun with both barrels with corresponding snap caps and pulled the trigger to see where the firing pin would strike. Both looked like it struck pretty much right in the center so I don't think that would be a problem at all.
Last thing to do is to bring it out to the range tomorrow and see how it performs. I'll post my results of the range trip after I get home.
Here is a video of me racking the slide using some snap caps to show how the slide was working. Overall the process was fairly simple to do and didn't take more than 15 minutes.
http://www.youtube.com/watch?v=xkoe_QqvogY