Anyone have any info on conversion barrels?

When the MPX debuted a couple years back , the press stated they could be convertible to .357 Sig or .40 readily

I'm jonesing for a 40 caliber carbine  (I over - purchased a bunch of 40 ammo at the tail end of '08 ) -- and the Sig really pushes all the right buttons

I'm thinking possibly since the intro, people were happy enough with the 9mm there hasn't been much demand , but IDK

No worries they'll be released real soon, Sig always follows through.

I'm sure the promised caliber exchange kit for my 556xi will be out any day now..

I bought it for 9mm, so IDK if cal conversions ever come.

I may not have all of the details exactly correct on this, but it depends if you have the Gen1 or Gen 2 upper. When the first MPX came out, Gen1, you were supposed to be able to swap calibers. Sig had to make some redesign on the upper. The Gen1 version will only be 9mm.

Gen 2 should be able to have a caliber conversion, but I have not seen barrels yet. Magazines are slightly different between the two versions. Even on their website they distinguished between the two magazine versions.  I thought those who bought the Gen1, when your serial number was verified, could get a special deal on purchasing a Gen2 upper. There have been some videos posted of the differences, even one by Sig.

That was some time last year. You would have to check with Sig customer service to see if these options still apply.

EDIT: I just looked at the 2017 catalog and there is no mention of any other caliber or barrel change. It lists 9mm only. Maybe there was no demand and it was dropped? I should be at the Great American Outdoor show next weekend in Harrisburg, PA. Sig should be there. Maybe I can get an answer then?

Gen 1 MPX will never get a caliber change. The Gen 2 is designed to accept one, it just hasn't been released yet.

SIG has said that although no conversion barrels will be available for Gen 1 uppers; they'll sell Gen 1 owners a complete Gen 2 upper  with barrel for the same price as a barrel alone.

Then additional conversion barrels can be installed in that upper receiver.

https://www.google.com/url?sa=t&source=web&rct=j&url=https://www.youtube.com/watch%3Fv%3DTp7WmEPyu_k&ved=0ahUKEwjs24iN8-3RAhXIOyYKHU8dBwwQwqsBCCAwAQ&usg=AFQjCNGdVFQCGUc4jhdfgFLGLfTSsnDrYg

None of that is ever going to happen.  The chances of the MPX being a modular platform are about the same as the 556xi.

At the Great American Outdoor Show in Harrisburg, PA, earlier this month, I spoke with one of the SIG reps about the MPX conversions. He did repeat the deal that if you have a gen 1 upper, you will be able to purchase a Gen 2 conversion kit and will get a full Gen 2 upper at the same time, as long as your serial number for the Gen 1 can be verified. He said the conversions kits ARE coming soon and he personally was pushing to have a conversion kit also released for a .22 caliber, besides the .357 and .40 that are planned. The Gen 1 upper will only ever be a 9mm.