Barrel diameter of M&P 9mm Pro?

[prickett]

I'm seeing something that I've not seen in ages: a heavily leaded barrel in my new M&P 9mm. I size to .357" and both my CZ and Sig like the rounds. The M&P does not. Are M&P barrels typically a larger inner diameter?

Thank god for an Outer Foul Out unit or I'd be scrubbing lead for weeks!

[upnorthwis]

I had the same problem. Leading so bad that steel wool wouldn't touch it. Finally solved it. Had to both powder coat and make a larger expander (.356) for Dillon 550B. That way I could shoot a .358 boolit and the brass wouldn't crush it down to a smaller dia.

[Catshooter]

No one knows the size of any one bore until it's measured.

I size to .3585 for my .356 Glock. If the boolits aren't heat treated they lead like crazy, even that large.


Cat

[runfiverun]

they may not be bigger in diameter.
but I'd bet it doesn't have a throat and the sharp start to the rifling is causing your issue.
look where the leading started...

[RJH]

I had one that I shot ww alloy .356 out of with no leading issues. Strange how that works.