converting .40 to 9mm

[bigkyle72]

I just picked up an M&P in .40. What do I have to do to convert it to 9mm? From what I have read its the 9mm magazines and a new barrel. I was wondering if it is just a 9mm barrel or a specific .40-9 conversion barrel.

[CK_32]

40 to 9 barrel. You may be able to run a stock 9mm barrel I know some guys do it with Glocks but its not good for either your barrel or slide.

I think lone wolf and storm lake just started coming out with 40-9 barrels for the M&P.

[taifei]

haven't seen lw conversion barrels for the m&p but wouldn't be surprised if they did. StormLake costs more but i see those available. Some people do run a stock 9mm barrel but it's looked down upon for safety and reliability reasons. There was talk about some timing or fitting (or both) issue that causes a lot of stress on the barrel when you use a stock 9mm instead of a conversion. Your hands are worth the $100-$130 imo.

Glock .40 mags can run 9mm in a pinch so I'd assume it would work with M&P mags as well. Don't see much of an issue if you're just slow shooting at paper. Might have a hickup here or there. Well used mags tend to lose a round when you pull it out of a pouch if you're sticking 9's into 40's.

[chrisf]

haven't seen lw conversion barrels for the m&p but wouldn't be surprised if they did. StormLake costs more but i see those available. Some people do run a stock 9mm barrel but it's looked down upon for safety and reliability reasons. There was talk about some timing or fitting (or both) issue that causes a lot of stress on the barrel when you use a stock 9mm instead of a conversion. Your hands are worth the $100-$130 imo.

Glock .40 mags can run 9mm in a pinch so I'd assume it would work with M&P mags as well. Don't see much of an issue if you're just slow shooting at paper. Might have a hickup here or there. Well used mags tend to lose a round when you pull it out of a pouch if you're sticking 9's into 40's.

No problem with the m&p. The added rounds is a plus. I'm not 100% on the legalities of that though. I never had a problem with the mags running 9 though.

[Zerorye351w]

I have a factory 9mm barrel for my M&P 40, haven't used it yet, but I have watched videos online that show functional results.

[xrayoneone]

The best way to do it is to get a complete slide assembly. You tend to loose extractor tension running 9mm barrel in a 40 due to the larger breach face of the 40. While it may work for competition I've seen them as being unreliable and would never trust one in a major match and diffinetly not as a defensive weapon.

I was going to go the barrel conversion route on my SIG ($250) but purchased a complete slide instead ($300). I'd start pricing slide assemblies.

[Slixxster]

I have a m&p 40c with stock 9mm barrel & stock 357sig barrel. All I did was barrel and mag. Shot 700rds+ with no issue. It's as accurate as my wife 9mm shield. One thing I recommend for the m&p is get the apex fss trigger kit and you'll be surprise.

[ArcherDog]

The M&P 9/40/357SIG handguns are identical except for the barrel and magazine, and the 40 cal magazines are co-labeled for 357SIG.

[Jet Setter]

Get a Storm Lake conversion barrel and some 9 mm mags. I would never suggest using a OEM 9 barrel. The specs are just slightly different enough that it could cause major safety issues. There are plenty of people who do it but is it worth the gamble?

[Josh3239]

For a true conversion you should change the ejector too.

[tectrry]

You should read the S&W forums, they have a thread about every month or two about this. But to add my own experience after reading the S&W forums I decided to use the stock 9mm barrel rather than the conversion barrel and it works flawlessly. I have put about 1000 rounds through it now without a single problem. As for the ejector, no need to change it - it is identical in both calibers. I typically shoot about 150 rounds a week of 9mm and then swap out the barrel at the range and shoot about 50 rounds of .40. The hardest thing is finding 9mm magazines.

[1911Luvr]

You should read the S&W forums, they have a thread about every month or two about this. But to add my own experience after reading the S&W forums I decided to use the stock 9mm barrel rather than the conversion barrel and it works flawlessly. I have put about 1000 rounds through it now without a single problem. As for the ejector, no need to change it - it is identical in both calibers. I typically shoot about 150 rounds a week of 9mm and then swap out the barrel at the range and shoot about 50 rounds of .40. The hardest thing is finding 9mm magazines.

^^^This.

I have a 9mm barrel for my 40 and no problems with it at all.

[tbc]

Do you have a 9mm mag yet?

A conversion barrel will cost you roughly $150 shipped. Two 9mm mags are very hard to get but you can still get them for $150 to $200.

The conversion will cost you at least $300 if you don't have the 9mm mags. A new gun is only $500.

Just something to consider.

[1911Luvr]

Do you have a 9mm mag yet?

A conversion barrel will cost you roughly $150 shipped. Two 9mm mags are very hard to get but you can still get them for $150 to $200.

The conversion will cost you at least $300 if you don't have the 9mm mags. A new gun is only $500.

Just something to consider.

My OEM S&W barrel was $66.99 at Midway and my mags were $33 each. That means the conversion cost me $133 to have the same capability as a new M&P 9. Sure, I bought more mags than that but in a far comparison it was less than half the $300 you mentioned.

[tectrry]

My OEM S&W barrel was $66.99 at Midway and my mags were $33 each. That means the conversion cost me $133 to have the same capability as a new M&P 9.

Just about the same for me - the mags I found were $40, but two mags and a barrel for under $150. can't buy another gun for that.