Difference between .40cal and .357?

ItalianBostonian

ItalianBostonian

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What is the difference between .40 and .357?

I have a m&p 40 and I guess you can change the barrel out and it wil let you shoot .357 rounds. Any one else do this?
 
yes. you can buy the M&P .357 sig barrel and swap it out. I have one for my M&P40. although I haven't shot it yet.

if you look at your mags, they should be marked 40 / 357....

you can also get 40 to 9mm "conversion" barrels from stormlake as well.

check the m&p pistols forum. i mainly lurk there, but it has some useful info

http://mp-pistol.com/boards/
 
Yea my mags do have 40/357 on them.
You can shoot 9mm out of the gun as well, I guess you would have to get new mags as well as the barrel?

So whats the difference between the .40 and .357 round?
 
The 357 is a 40 case necked down to 357. There seems to be a minor difference in overall length - my Glock 27 converted to 357 with the 40 mags. I never switched it to 357, but my factory Sig 2340 mags are marked both 40 and 357.

If I remember right, Sig was trying to get the same ballistics performance as a 125 gr 4" 357 mag out of a semi-auto. I think they got close, but I wasn't able to find any data from a 4" 357mag to compare to the Sig - just 6".
 
You can shoot 9mm out of the gun as well, I guess you would have to get new mags as well as the barrel?
Click to expand...

i have a lonewolf barrel, 40 to 9mm conversion for my Glock 23.

it works fine with the .40 mags, but I did pick up 2ea., 10rd 9mm mags.

it's been flawless.

the only with shooting it are erratic ejection patterns with the 9mm. other than that, it's great! saves a little bit on $$$ shooting 9mm & you don't have to buy the same gun in different caliber (i.e. Glock 19 or M&P9).

*note: most of the reading I've done on glocktalk and m&p-pistols forum advise NOT to CCW w / conversion barrels, but i can honestly say I would if i had to.
 
To answer the original Poster's question about the ammo....

.40 S&W vs. .357 SIG

Both Casings are the same outer diameter dimension as well as effective overall length. Beyond that, they are different.

The .357 SIG necks down to hold a 9mm bullet (.355") and the casing itself is slightly thicker in the head end (it is not a modified .40 S&W, but a new design that is actually stronger than the .40 S&W)

Also, nothing else sounds the same as a .357 SIG firing. I don't care what gun you are shooting from, it has a totally different report than anything else I've heard.

Drop-in barrels generally work just fine as do the .40 S&W magazines for both rounds. Some manufacturers develop a unique .357 SIG magazine which will not feed .40 S&W, but this is limited to SIGARMS from what I've seen. Since the head and rim of the two rounds are virtually identical in their external dimensions, the action of the gun works just fine.

While I've seen .40 S&W mags feed 9mm jut fine into a conversion barrel, I HIGHLY recommend you take extreme care in following this practice. You do NOT want to ever chamber a 9mm into a .40 S&W or .357 SIG barrel. The result could be disastrous. .357 SIG into a .40 Barrel is also not a good idea, but at least it isn't likely to blow up on you.
 
KMM696 said:
If I remember right, Sig was trying to get the same ballistics performance as a 125 gr 4" 357 mag out of a semi-auto. I think they got close, but I wasn't able to find any data from a 4" 357mag to compare to the Sig - just 6".
Click to expand...

Yes. They wanted .357 magnum performance out of an cartridge that would fit in a conventional semi-auto.

The 125 grain loads in .357 SIG actually out-perform .357 magnum in the same barrel length. Heavier bullets don't work as well in .357 SIG.

It is loud as heck, it feeds more reliably since it's necked, and packs a ton of punch for it's size.

All three of my carry guns are in .357 SIG.
 
Chris said:
Drop-in barrels generally work just fine as do the .40 S&W magazines for both rounds. Some manufacturers develop a unique .357 SIG magazine which will not feed .40 S&W, but this is limited to SIGARMS from what I've seen. Since the head and rim of the two rounds are virtually identical in their external dimensions, the action of the gun works just fine.
Click to expand...

Some Glock .357 SIG mags can't be loaded all the way with .40 ammo due to the slightly different slant of the follower, but most of them will work fine.
 
Some people say that Sig came up with the .357 Sig round to try to get the wheel gun and Dirty Harry types to move on over to the semi automatics.

40 S&W to .357Sig and visa versa is a simple swap. The 9mm conversion seems to have extractor issues.

The .357Sig is a sweeeet load and if you have an extra 125 or so kicking around buy the aftermarket barrel and try it out. Even the Glock factory barrels can be had for short money online if you shop around.
 
Well, I picked up a Sig 239 in 357 yesterday, so I guess I'll be finding out for myself. [smile]

Can't get to the range until Friday, though.

[sad]
 
The original thrust for design of the .357sig round was to put .357 magnum performance in a semi-auto package. Guns like the Desert Eagle that shot the 357 mag were just not practical as a carry gun for law enforcement.

the 357sig round operates are a much hiigh presssure than .40sw round. This is what causes the extra loud bang.

the 357sig round is also designed to penetrate soft surfaces like body armor and clothing better than a .40sw. It has been reported in one incident that LE shot through the door of a tractor trailer at the driver. the .40 round would not penetrate through the inner steel as it had already deformed, while a 357sig round went straight through and made the kill.

Good article on Wikipedia explaining everything. Just search for 357sig

It can be debated 10000000 ways as to which one is more effective and you will get 1000000 different opinions.
 
I have owned both 40 and 357Sig barrels in a P239. The 357Sig is way more accurate, is louder, but kicks a bit less. I think the extra noise fools a lot of shooters into thinking it kicks harder as well, but it doesn't. Shoot them side by side in the same gun and you will agree. It is similar to the 135gr Corbon .40S&W.

Working on getting a 4" 357Sig barrel for my M&P40c. Can't wait.
 
Xak said:
I have owned both 40 and 357Sig barrels in a P239. The 357Sig is way more accurate, is louder, but kicks a bit less. I think the extra noise fools a lot of shooters into thinking it kicks harder as well, but it doesn't. Shoot them side by side in the same gun and you will agree. It is similar to the 135gr Corbon .40S&W.

Working on getting a 4" 357Sig barrel for my M&P40c. Can't wait.
Click to expand...

I didn't notice a difference in recoil shooting .357 SIG and .40 side by side out of Sigs, but I did notice it out of Glocks, especially in the G27/G33.
 
GSG said:
I didn't notice a difference in recoil shooting .357 SIG and .40 side by side out of Sigs, but I did notice it out of Glocks, especially in the G27/G33.
Click to expand...

glocks are beasts! my hat goes off to you guys who carry those sub-compact glocks in anything higher than 9mm.
 
jay_chris said:
glocks are beasts! my hat goes off to you guys who carry those sub-compact glocks in anything higher than 9mm.
Click to expand...

I only carry it when I can't conceal the G32, which means it lives in the safe all winter and lives in my pants all summer. [laugh]

I used to carry a S&W Airweight snubbie in the summer, but nine .357 SIG's and a 15 round reload is much better than five .38's with a speedloader in my book, and I have a lot fewer rust issues.
 
I carry in .357SIG on occasion and whether plinking with it or testing out carry ammo, have found it to be a great round.

Its nice to see a thread on it sans the debate on the worthiness of the round.

Its has Chris mentions a great report on the range, nothing really sounds like it and its top notch all around. I hear reloading it is a pain however.
 
clinotus said:
I carry in .357SIG on occasion and whether plinking with it or testing out carry ammo, have found it to be a great round.

Its nice to see a thread on it sans the debate on the worthiness of the round.

Its has Chris mentions a great report on the range, nothing really sounds like it and its top notch all around. I hear reloading it is a pain however.
Click to expand...

In what kind of gun?

hollewud7 said:
how much does 100rds for wwb 357 sig cost?
Click to expand...

About 50 cents a bullet. Seriously. I just bought two boxes of 50 WWB FMJ .357 SIG for $23.97 a box.
 
Yep, there is nothing quite like the .357sig, it is a spendy round to practice with unfortunatly.

I carry it occasionally when Im rocking my HKP2000, but only when Im dressed appropriatly.
 
I can't wait to shoot my .357sig glock 33. I got it about a month ago and have haven't made it to the range yet.
 

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