Convert 40 to 9?

[Rookie]

So I and some ROs were talkin the other day at the range about 40s&w passing into history. When I retired 12 years ago the entire nation of LEOs carried 40s, not so anymore. Anyway one RO mentioned that I could convert my old duty S&W M&P Pro from 40 to 9 by just by dropping in a 9mm barrel with same mags and recoil spring so I ordered a factory 9mm barrel from Numrich. Outside dimensions looked identical.

Had a chance take it to the range today. I was surprised to see POI = POA with the new barrel and it shot a nice group, infact the first 4 rounds went in the same hole at 7yds with my crummy reloads.

The other cool thing was that mags that hold 15 rounds of 40 will now hold 19 of 9mm.

However it would jam every 6 to 8 rounds. Live rounds would fail to feed. Looked like a stovepipe but with a live round not spent.

My first thought was how much higher the top smaller rounds sits in the lips could be the cause of the round popping out of mag too quick. Here's some pics to compare.

First is 9mm, second is 40 in same mag.

What Do you guys think? Should I snag some 9mm mags? Change recoil spring? Or scrap the whole idea?

 

[Sniperwannabee]

I did the swap 5 yrs ago with my m&p and just bought the mags and the barrel. No problems ever

 

[Rookie]

Current recoil spring is a Wolfe with less than 500 rounds of 40 on it.

 

[Redmanss]

With the cost of a new pistol around $600-ish (or lower) and the ability to sell the old pistol for $400-ish, I see absolutely zero reason to try to convert over in anything where utmost reliability is a priority.

Autos want to feed what they were made for, and only what they were made for.

 

[Rookie]

Selling guns is against my religion!

 

[DocRDS]

Good mags are the heart of any pistol.

Get dedicated 9 mags.

And shoot a 1911 already pussy. They make double stack ones in 9mm anyway.
TWO WORLD WARS!
(it is the bear pit)

 

[Redmanss]

Selling guns is against my religion!

Then keep it and buy a 9. I stand by what I said though, if it’s anything more than “Hmm, wonder if I can make this work…”, I wouldn’t bother and I absolutely wouldn’t carry it for self defense.

ETA: The 40 S&W isn’t going anywhere, that’s a myth. Cops quit carrying .38 SPL 40 years ago, still all over the place.

 

[Maggot]

Then keep it and buy a 9. I stand by what I said though, if it’s anything more than “Hmm, wonder if I can make this work…”, I wouldn’t bother and I absolutely wouldn’t carry it for self defense.

ETA: The 40 S&W isn’t going anywhere, that’s a myth. Cops quit carrying .38 SPL 40 years ago, still all over the place.

Gotta agree with Red. New is usually better than fucked with. You can pick up a nice, stock, 9 for $600 anytime. Probably for less this was just my first pick. I always carry a 1911 but this would be my next choice. In fact I bought one.

Walther PDP Compact Optic-Ready Semi-Auto Pistol​

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Walther PDP Compact Optic-Ready Semi-Auto Pistol ; Sale. $599.00$649.99. SAVE $50.99 ; Online Firearm Orders. Select firearms are able to be ordered online and ...

 

[Rookie]

That's true Redman. My first duty gun was mod 66 and I was one of the last holdouts to give it up for a 9mm. Still have a few 38s around but never shoot em.

 

[Rookie]

Thanks Doc! I do love my 1911 in the Lord's caliber.

 

[Redmanss]

Just read your OP again that you're tinkering with your old duty pistol, absolutely wouldn't sell that one or anything with an actual positive history behind it.

I sold my old Sig P229 40, but it was a Christmas present from my ex back when we were still married. I didn't want to even look it, sentimental value was in the negatives.

Mags will likely take care of the feeding issue, but you may still run across ignition and extraction issues because of the smaller case head difference going to 9mm. You may need a reduced recoil spring as well, depending on just how old the current one is.

 

[wvfarrier]

I wish I could upsize from 9 to 40.

 

[AMGtuned]

my 40s&w! 180gr Hydra-Shok FTW!

 

[34vld]

Bend your lips in first

 

[The D]

I wish I could upsize from 9 to 40.

This is why you always plan ahead. Buy guns in .40 and then buy conversion barrels in 9mm. That’s what I did with my super ultra mega scary ghost gun, built a G27 first then bought a 9mm conversion barrel and 9mm pmags

 

[atomic41]

What Do you guys think? Should I snag some 9mm mags? Change recoil spring? Or scrap the whole idea?

If you are just bored and playing around then sure mess with it for fun but if you are doing this as a real thing then scrap the idea. The 40 is way cooler and has a history. I have my dad's first duty pistol (S&W .357) and my son bought his first duty pistol (G17) from his dept. that he plans to do some laser engraving on. Keep it stock and in the family man.

 

[Makinchips208]

So I and some ROs were talkin the other day at the range about 40s&w passing into history. When I retired 12 years ago the entire nation of LEOs carried 40s, not so anymore. Anyway one RO mentioned that I could convert my old duty S&W M&P Pro from 40 to 9 by just by dropping in a 9mm barrel with same mags and recoil spring so I ordered a factory 9mm barrel from Numrich. Outside dimensions looked identical.

Had a chance take it to the range today. I was surprised to see POI = POA with the new barrel and it shot a nice group, infact the first 4 rounds went in the same hole at 7yds with my crummy reloads.
View attachment 8325798
The other cool thing was that mags that hold 15 rounds of 40 will now hold 19 of 9mm.

However it would jam every 6 to 8 rounds. Live rounds would fail to feed. Looked like a stovepipe but with a live round not spent.

My first thought was how much higher the top smaller rounds sits in the lips could be the cause of the round popping out of mag too quick. Here's some pics to compare.
View attachment 8325806
First is 9mm, second is 40 in same mag.
View attachment 8325808
What Do you guys think? Should I snag some 9mm mags? Change recoil spring? Or scrap the whole idea?

Gotta get new mags.

New barrel and new mags will do it. Box up the old 40 stuff for a rainy day.

May possibly need recoil spring, but if it functions fine yer gtg.

But it’s a perfect excuse to get a new pistol and just keep the 40 as a 40.

 

[Rookie]

This 40 was my last duty weapon and the only one that I purchased. It is special to me. Will keep the 40 cal parts for sure. I bought a 9mm mag From Munrich today so will see how it works. If it does I will buy more. Ideally this will be a convertible to whichever cal ammo is available for.

 

[Ronws]

Some years ago, I bought my M&P M2.0 in 9 mm with the 4.25 in barrel in a range kit. It came with 3 mags, a right handed holster, and 2 mag carrier. The mags hold 17 rounds. I still carry that today. It is my EDC in an OWB holster under a large angler's shirt or jacket.

That whole kit, including the range case it came in was 675 at Shoot Smart, with 3 locations. I got it at the store in Grand Prairie, (Tx.) Originally, I was going to get a 40 because I saw an ad from Academy that model in 40 on sale. My boss convinced me to get a 9. Everyone and his aunt makes ammo for 9 mm. It's just as effective.

As my LTC instructor said, "I have a 1911 in .45 ACP, a .380, and a 9 mm. Which one do you want me to shoot you with?"

Anway, I digress. It depends on what you want. If you want to pursue the conversion, do what makes you happy.

 

[wvfarrier]

This is why you always plan ahead. Buy guns in .40 and then buy conversion barrels in 9mm. That’s what I did with my super ultra mega scary ghost gun, built a G27 first then bought a 9mm conversion barrel and 9mm pmags

Sadly the two I wish were 40s ONLY come in 9mm

 

[Maser]

I carry a DA revolver. What are these jams you speak of?

 

[chevy_man]

I carry a DA revolver. What are these jams you speak of?

It's similar to when you get a piece of dirt in there that keeps the hand from engaging, the trigger from moving, or seizes it all hard.


Look at the moving parts on an auto vs a wheel gun. I'll take the auto after having hand fit my own parts in old wheel guns that came out of time.

 

[Father O’blivion]

It's similar to when you get a piece of dirt in there that keeps the hand from engaging, the trigger from moving, or seizes it all hard.


Look at the moving parts on an auto vs a wheel gun. I'll take the auto after having hand fit my own parts in old wheel guns that came out of time.

The revolver is probably heavy enough to beat someone to death though.

 

[Makinchips208]

I carry a DA revolver. What are these jams you speak of?

What is this DA you speak of?

Single action only.

 

[chevy_man]

The revolver is probably heavy enough to beat someone to death though.

Metal things hurt when hit with them.

Gives you enough time while they're confused you just hit them with a shooty thing, to stab them while they're contemplating getting hit with a gun upside the head.

 

[LeftyJason]

Gotta agree with Red. New is usually better than fucked with. You can pick up a nice, stock, 9 for $600 anytime. Probably for less this was just my first pick. I always carry a 1911 but this would be my next choice. In fact I bought one.

Walther PDP Compact Optic-Ready Semi-Auto Pistol​

View attachment 8325836
Cabela's
https://www.cabelas.com › Home › Shooting › Guns



View attachment 8325837
Walther PDP Compact Optic-Ready Semi-Auto Pistol ; Sale. $599.00$649.99. SAVE $50.99 ; Online Firearm Orders. Select firearms are able to be ordered online and ...

My next is going to be that exact one but threaded as well. Still going to keep my m&p9c gen 1 and my full size 9mm (sti gp6). That Walther more replicates the slide release from the gp6.

 

[Maggot]

My next is going to be that exact one but threaded as well. Still going to keep my m&p9c gen 1 and my full size 9mm (sti gp6). That Walther more replicates the slide release from the gp6.

If you like the way a 1911 fits your hand you'll love the Walther, Great factory trigger as well.

 

[LeftyJason]

If you like the way a 1911 fits your hand you'll love the Walther, Great factory trigger as well.

Haven't really shot a 1911. Blasphemy I know.

My 9c has the apex forward set sear and trigger with 4.5lb spring. The gp6 has a better factory trigger than that. Gp6 is older (circa 2008) grand power k100 mk6.

Recently took my FIL to a local renting range. We both tried a G19, Sig 320, hkvp9, Cz p0? hammer, Springfield x?, my m&p9c, Walther pdp full size, and a fn50?. All in 9mm. He did not like the Glock and liked the Cz, Hk, and Walther the best. I liked the Walther the best. Hk isn't available factory optics cut and threaded. Walther has good slide release. My gp6 you can slide in a fully loaded mag and it will drop the slide (long pivot arm). Gp6 not OC or capable to thread per factory. Rotating lock barrel.

Sorry @Rookie for the thread derail.

 

[Rookie]

No worries Lefty threads have a way of doing that. I will bring it back after I try the pistol with a 9mm mag.

 

[Rookie]

To update, received the 9mm mag today and hit the range. 9mm swap works perfect with defensive rounds and my crummy reloads. POI=POA. So cal swap for $170 beats $600 for new gun. Plus the versatility of 1 gun, 2 cals.

 

[_Windrider_]

40 to 9. Isn’t that what 357 sig is. 40 cal casing necked down for a 9mm bullet.

 

[918v]

40 to 9. Isn’t that what 357 sig is. 40 cal casing necked down for a 9mm bullet.

Have you even looked into the ballistics between the two?

 

[Rookie]

Who the heck shoots or reloads 357sig? That's a dead cal in my book.

 

[_Windrider_]

Have you even looked into the ballistics between the two?

I was just asking a question. Sheesh.

 

[Rookie]

I remember when the dept allowed guys to carry 357sig and a box of factory ammo would have a few crushed necks.

 

[_Windrider_]

Who the heck shoots or reloads 357sig? That's a dead cal in my book.

I think the SS still uses it.

 

[918v]

So I and some ROs were talkin the other day at the range about 40s&w passing into history. When I retired 12 years ago the entire nation of LEOs carried 40s, not so anymore. Anyway one RO mentioned that I could convert my old duty S&W M&P Pro from 40 to 9 by just by dropping in a 9mm barrel with same mags and recoil spring so I ordered a factory 9mm barrel from Numrich. Outside dimensions looked identical.

Had a chance take it to the range today. I was surprised to see POI = POA with the new barrel and it shot a nice group, infact the first 4 rounds went in the same hole at 7yds with my crummy reloads.
View attachment 8325798
The other cool thing was that mags that hold 15 rounds of 40 will now hold 19 of 9mm.

However it would jam every 6 to 8 rounds. Live rounds would fail to feed. Looked like a stovepipe but with a live round not spent.

My first thought was how much higher the top smaller rounds sits in the lips could be the cause of the round popping out of mag too quick. Here's some pics to compare.
View attachment 8325806
First is 9mm, second is 40 in same mag.
View attachment 8325808
What Do you guys think? Should I snag some 9mm mags? Change recoil spring? Or scrap the whole idea?

I wouldn’t carry that gun for self defense. The 9mm has a smaller case and a lot more diameter variance than the 40, from brand to brand. You could end up with less than ideal extractor hook purchase on the case for reliable extraction. It’s fine for a range gun tho.

 

[Rookie]

That has to be true on some level. I won't trust it before I have a crap ton of rounds through it.

 

[Father O’blivion]

To update, received the 9mm mag today and hit the range. 9mm swap works perfect with defensive rounds and my crummy reloads. POI=POA. So cal swap for $170 beats $600 for new gun. Plus the versatility of 1 gun, 2 cals.

So no problems extracting? I thought I read somewhere that there would be an issue of the 40 extractor not working on a regular 9 barrel.

 

[Rookie]

Not so far but only 155 rounds fired

 

[The D]

So no problems extracting? I thought I read somewhere that there would be an issue of the 40 extractor not working on a regular 9 barrel.

As far as Glock conversion barrels go, my understanding is that the earliest barrels were the ones that had problems. After a few rounds of modifications and beta testing in the wild it’s been ironed out. I don’t have a ton of rounds through my P80 fake Glock but I haven’t had any problems attributed to the barrel

 

[Inifinty]

First we gotta manbun the .30 rifle. And now we are manbunning the .40 handgun too?

At least you get something more out of the 6.5 creedmoor. Stop being pussies.

Mah recoil.

 

[iceng]

.357 SIG - Wikipedia

en.m.wikipedia.org

40s&w case, necked to 9mm.

Feeds off your 40cal magazine, no extraction or ejection issues, and you still have to change the barrel.

Ill see myself out..

 

[Bantam1]

I know this thread has been about the M&P but I was gifted a Glock gen 2 23 in .40. I did the 40-9 KKM barrel conversion and had to change the trigger housing because of the ejector difference. Of course I have to use my 9mm mags.

The pistol has been flawless and zero issues with those small changes. The striker is even stamped .40 which I found odd. I can't see any difference between it and my other Glock strikers in 9mm. The extractor was the same from what I could measure. I tossed a new stock recoil spring and rod in because I had no idea how many rounds were on the original. I'm happy with the conversion. I don't mind recoil or the .40. I just didn't have anything in it at the time and had lots of 9mm Glock stuff on hand. My buddy owns a 23 so I gave him all the mags.

 

[Rookie]

I didn't do the conversion because of 40cal recoil. I have over 25,000 45acp rounds through my 1911 from IDPA shooting. Recoil is not a problem. I do like the versatility of 2 cals in 1 gun. I have an XDm with several hundred dollars in Apex upgrades. Also with thousands of 9mm rounds fired with zero issues. My only complaint is the location of the slide release that interferes with my grip. The better ergonomics of the N&P led me to considering the conversion.

My concern is, reliability has to be negatively impacted at some level, I think. Maybe the extractor is just under less tension while holding the smaller rim but still sufficient? If there is lateral variances in where the case sits against the breachblock could the ejector miss hitting the case causing a failure to eject?

 

[Rookie]

Check out these pics showing 40cal rounds held by the extractor against the breachblock, no barrel.

 

[Rookie]

Now compare to how loosely 9mm rounds are held. In fact the 9mm will fall out if not held there by me.

 

[Rookie]

Also never noticed that the rim on 40cal is thicker than 9mm until now. I measure the 9mm at .040 and 40cal at .052.

 

[Makinchips208]

I didn't do the conversion because of 40cal recoil. I have over 25,000 45acp rounds through my 1911 from IDPA shooting. Recoil is not a problem. I do like the versatility of 2 cals in 1 gun. I have an XDm with several hundred dollars in Apex upgrades. Also with thousands of 9mm rounds fired with zero issues. My only complaint is the location of the slide release that interferes with my grip. The better ergonomics of the N&P led me to considering the conversion.

My concern is, reliability has to be negatively impacted at some level, I think. Maybe the extractor is just under less tension while holding the smaller rim but still sufficient? If there is lateral variances in where the case sits against the breachblock could the ejector miss hitting the case causing a failure to eject?

A 9mm case rim diameter is 0.88mm (0.033”) smaller than a 40 cal case rim diameter.
Upon extraction the case will be held centered in the chamber, so extraction will probably be ok.
As you can see you have a looser fit, and obviously there is the potential for ejection issues of the spent case.
Observe how and where the cases go compared to normal.

9mm in my Glock 9mm looks similar to your 40 in a 40 cal slide.

 

[Rookie]

Obviously the barrel should keep the round centered and pushed hard against the breachface when in battery. Sure gonna be loose goosy during extraction and ejection.

Only more rounds fired will prove reliability or lack thereof. I may call Smith to get their thoughts but seems to me ultimate reliability could only be achieved with a tighter extractor.