View Full Version : New M&P Barrel doesn't fit

11-29-2012, 7:47 PM
I bought a new barrel for my M&P 45 full size. It's a threaded barrel that came out of another M&P fullsize.

It fits fine in the slide, but when I try to put the slide on it stops cold right when the slide is starting to go on the rear rails. My guess is some part of the bottom of the feedramp is hitting the frame where the lug would normally catch to unlock the barrel.

Any ideas other than sending it to S&W to be fitted or anyone familiar with this kind of issue?

For those questioning the threaded barrel, I moved out of state, but find this to be the most knowledgeable gun board so I still frequent it.

11-30-2012, 8:21 AM
How do the 2 barrels compare side by side, if you can't tell any difference between the 2 then double check the recoil spring, sometimes it slips out of place or gets crooked when putting the slide back on.

I have the same FS M&P in .45 & the only way I can make mine do what yours is doing is, If reassemble it holding on to the front of the slide & I push down to hard which raises the rear of the slide up enough that it won't go onto the rear slide rails.

If you don't find the solution here on CG, post up on the M&P Forums (http://mp-pistol.com/smith-wesson-mp-forums.php) lots of knowledgeable M&P fanatics over there.

Best of luck, Lee

11-30-2012, 5:16 PM
Thanks Lee. First thing I thought was the recoil spring. I'll play with it more tonight and see if I notice anything else.

12-01-2012, 7:29 AM
Well I figured it out. The top of the barrel where it meets the chamber is hitting the underside of the slide. Using my micrometer there is a .005" difference in the distance between the top of the barrel and the top of the chamber between the two barrels. The top of the .45 barrel that came with the pistol is a slight flat spot which was probably part of the fitting process whereas the new barrel didn't have that. So, it looks like taking a few thousands of with a file will make it fit and allow the ramp to clear what it is hitting on the frame.