40 to 9 Conversion

[Hatrix]

I know it's probably been asked before, so please forgive my inability to do the search. I'm lazy like that!

Can I use a S&W Factory 9mm barrel and 9mm mags in my M&P 40's slide without any issues? Or is there a big difference between the size/outside diameter of the 9mm barrel vs the 40?

I know Storm Lake makes their conversion barrels, but they're never in stock and kind of pricey. I would also like to stick with S&W parts if possible.

Thanks in advance, and feel free to beat me with a big stick for asking something that's probably very redundant.

 

[OKFC05]

Yes. and yes

 

[Hatrix]

Awesome. Thank you.

 

[pfurrer]

It's my understanding the M&P 40 was developed first and the M&P9 was built on the same frame. The difference being a 9 barrel and mag.

 

[MSG Glenn]

A couple of weeks ago I was talking to S&W customer service about another matter & asked him about ordering 9MM & &.357 SIG barrels for my 40C. He told me that they weren't taking orders for barrels at this time & didn't know when they would.

If you find that they are let me know. I'd just as soon have factory parts, too.

 

[Rastoff]

I bought my factory 9mm barrel from Midway USA. It cost about $65 at the time. They have been out of stock for months now though.

You may have to go with Storm Lake or KKM for now.

 

[AwfAxis]

I'm wondering if the extra slop where the barrel hood mates with the slide reduces accuracy; specifically when you put a stock 9mm barrel into a 40 slide.

However, for $165, a KKM 9mm conversion is reasonable.

On a related note, I purchased a KKM 40 barrel for my new 40L, and am having the stock 40 barrel's hood thinned in order to fit my 9L CORE slide.

 

[scattershot]

I purchased a factory barrel from Midway, and a 9mm mag. Everything dropped right in, and I have had no problems at all.

 

[Rastoff]

I'm wondering if the extra slop where the barrel hood mates with the slide reduces accuracy; specifically when you put a stock 9mm barrel into a 40 slide.

It absolutely will. The lock up between the slide and barrel is the critical component of accuracy. If the lock up is not tight, then it has the effect of the sights moving every time you shoot.

The M&P lock up is completely done at the chamber/slide interface. The barrel touches the slide at the muzzle, but that isn't the critical component of the lock up. Even so, the barrel should not move at all once the slide is forward.

 

[Mydogmax]

Don't know that much about the 40 to 9 conversion, but thought that on the conversion kit that the 9mm barrel outside diameter was the same as the 40. The inside diameter is smaller. I think I saw it on YouTube.

 

[alde]

What about the diameter of the shell in relation to the extractor and ejector? The 9mm shell is quite a bit smaller in diameter than the 40/375 Sig.

 

[mkbruce]

What about the diameter of the shell in relation to the extractor and ejector? The 9mm shell is quite a bit smaller in diameter than the 40/375 Sig.

Extractor and ejector are the same parts for 40/357 and 9.

 

[Rastoff]

What about the diameter of the shell in relation to the extractor and ejector? The 9mm shell is quite a bit smaller in diameter than the 40/375 Sig.

I thought this would be a problem as well. However, it seems that S&W uses the same breech face and extractor for the 9mm guns.

I just measured the external chamber dimensions of both 9mm and .40S&W factory barrels. They are identical. Therefore, the 9mm and .40 slides are the same as well. This is why the extractor doesn't need to be changed. It must just move out a little more when shooting .40S&W.

 

[alde]

That's good info on the extractor and ejector. Now to find a barrel and a couple of magazines.

 

[uechikid]

As has been stated above, you can just drop in an 9mm barrel and mag and you're good to go. My wife has been using the 9 conversion in her M&P40c most of this year with no issues. I took my son in law out for the first time last weekend with a 9mm setup in my 40 FS. Between the two of us we shot about 150 rounds, again, with no issues.
Midway has mags. If you are going to do this I'd get a couple of mags while you can.
http://www.midwayusa.com/product/86...nd-p-9mm-luger-10-round-steel-blue?cm_vc=S014

 

[uechikid]

It absolutely will. The lock up between the slide and barrel is the critical component of accuracy. If the lock up is not tight, then it has the effect of the sights moving every time you shoot.

The M&P lock up is completely done at the chamber/slide interface. The barrel touches the slide at the muzzle, but that isn't the critical component of the lock up. Even so, the barrel should not move at all once the slide is forward.

There is an ever so slight difference in how the two barrels fit. The 9 barrel in the 40 slide has about a 1/64" amount of play. I would agree that this can affect accuracy, but I just put 75 rounds through mine and at 15 yards I was inside of 8" 68 times and I'm no marksman. For HD I'd say that's pretty good.

 

[rsrocket1]

It absolutely will. The lock up between the slide and barrel is the critical component of accuracy. If the lock up is not tight, then it has the effect of the sights moving every time you shoot.

SHHHHHH!
Don't tell that to my M&P40 -> 9 with the S&W Factory barrel. It doesn't know any better!

12 yards left target standing, right target sitting at the table with the gun resting on the table top.

 

[Sgt 45]

OK I gather you can do the .40 to 9mm, how about the other way around?

 

[mtnwinds]

I installed a 9mm factory barrel in my M&P 40FS and my wife used it the next day to qualify for her CHL.

I would not recommend converting a 9mm pistol to 40. That would require milling the sides of the 40 barrel to fit the 9mm slide, effectively reducing the thickness of the chamber walls. If I wanted that conversion I would buy a 40 slide assembly.

 

[Sgt 45]

Sounds reasonable. Not that I can shoot a .40 anyway, the wrist is just getting too old for the sharp recoil.