M&P40 to 9mm Conversion

[chekmate]

I tried searching for an answer but couldn't find one to my specific question. I understand you can convert an M&P40 by simply swapping out the 40 barrel for a factory 9mm barrel or StormLake 9mm barrel. My questions are as follows:

1. Is accuracy affected when using a 9mm barrel in an M&P40?

2. What is the difference between factory and StormLake 9mm barrel?

3. Will I still be able to drop in a 9mm barrel in my M&P40 even though I changed to an APEX FSS polymer trigger?

4. I read that you can still continue to use the mags that come with the M&P40 when you drop in a 9mm barrel? Is this safe to do?

Thank you.

[fullmd]

1 no effect that I've seen in terms of accuracy.
2. I got the factory barrel works just fine. But i heard that the stormlake barrel could cause jams
3. Idk sorry....

[fullmd]

4. Yes you can. Last round may not feed properly... Just get the 9mm magazine they're becoming available again

[fmunk]

1. Is accuracy affected when using a 9mm barrel in an M&P40?

No. External dimensions are the same.

2. What is the difference between factory and StormLake 9mm barrel?

Twist rate.

3. Will I still be able to drop in a 9mm barrel in my M&P40 even though I changed to an APEX FSS polymer trigger?

Of course. Apex sear kits are more finely polished to remove grittiness in trigger feel/travel while the trigger itself changes geometry to reduce travel and over-travel. All of the mechanics required to fire ammunition remain unaltered.

4. I read that you can still continue to use the mags that come with the M&P40 when you drop in a 9mm barrel? Is this safe to do?

It might work, but for most reliable operation, stick with 9mm magazines when shooting 9mm. The followers are different.

[LBDamned]

if you aren't in a hurry, sign up for "notify me"

http://www.midwayusa.com/product/150824/smith-and-wesson-barrel-s-and-w-m-and-p-9mm-luger-425?cm_vc=ProductFinding

http://www.midwayusa.com/product/862846/smith-and-wesson-magazine-s-and-w-m-and-p-9mm-luger-10-round-steel-blue?cm_vc=ProductFinding

that's what I did (barrel was in stock at the time though... but mags took a little while) works perfect - it's exactly the same as buying an M&P 9.

[Hope59]

[chekmate]

Thanks to everyone who responded. Looks like getting the 9mm barrel and mags will be my next purchase.

[FX-05 Xiuhcoatl]

I converted my m&p40 to 9mm over 1 1/2 years ago, drop in factory 9mm barrel, factory 9mm magazines and 2000+ rounds later it still shoots like a dream, never had FTF or FTE.

[brian5271]

The 40 cal and 9mm barrels are not the same dimensions. If you don't believe me, try using a 40 cal barrel in a 9mm pistol. It doesn’t work. The tang at the rear of the chamber hood is not the same size. Many people have successfully used 9mm barrels in 40 M&P's without issue, but there have also been many that have had issues. If it were me, I would spend the little bit extra money and get the conversion barrel. The Storm Lake is the same size as the factory 40 cal.

Here is a link to the M&P Forum, there is lots of good info here: http://mp-pistol.com/

[uechikid]

If you're going to do this 44mag.com has 9mm mags in stock. Their web site says they have 15. M&P 9mm mag were very hard to come by just a few months ago. I saw them going for upwards of $100 each on eBay. Buy the mags while you can. It looks like there getting scarce again.

http://www.44mag.com/product/698/smith_and_wesson

[LBDamned]

The 40 cal and 9mm barrels are not the same dimensions. If you don't believe me, try using a 40 cal barrel in a 9mm pistol. It doesn’t work. The tang at the rear of the chamber hood is not the same size. Many people have successfully used 9mm barrels in 40 M&P's without issue, but there have also been many that have had issues. If it were me, I would spend the little bit extra money and get the conversion barrel. The Storm Lake is the same size as the factory 40 cal.

Here is a link to the M&P Forum, there is lots of good info here: http://mp-pistol.com/

op asked about 40 to 9, not 9 to 40...

OEM 9 barrel and mags fit and fires perfect in my 40 frame...

[AwfAxis]

There are differences in the breach face in terms of the tang at the top of the barrels. There is an opening of groups which becomes apparent at 25 yrds using a 9mm barrel in a 40 slide.

I run an M&P 40 for USPSA Ltd-Mjr, but for other venues, put in my KKM 40-9 conversion barrel. The fit is better than the factory 40 barrel in terms of lock-up. No wiggle.

Putting in a factory 9mm barrel, you have some play (horizontal). For most practical purposes, this isn't significant, but at a distance beyond 15 yrs, it is.

If you need long shot accuracy, add a conversion barrel to your purchase of 9mm mags.

KKM's typically ship next day if ordered from their website.

[LBDamned]

For competition shooting it makes perfect sense to spend $$$ on an aftermarket conversion barrel... But for general use the majority of shooters are fine with a $70 OEM 9mm barrel.

I generally shoot 7-20 yards and the 9 barrel is as accurate as the 40 for me... I suppose a proficient comp shooter might see a difference - but precision comes at a cost.

I've had no failures using 9 in 40

[brian5271]

op asked about 40 to 9, not 9 to 40...

OEM 9 barrel and mags fit and fires perfect in my 40 frame...

I read what he asked ... Did you read what I wrote?

I said that the 9mm and 40cal barrels are not the same dimensions, and they are not.

[bruss01]

I got the Storm Lake for my 40>> 9mm conversion.

No issues with accuracy or fit.

I use the 9mm magazines when shooting 9mm ammo. I tried the .40 mags and while they did "work" they weren't what I would call reliable.

I have the Apex kit including extractor upgrade but have not installed it yet. The trigger on my M&P really sucks, but I love everything else so far.

This conversion is a winner in my book.