M&P40c, making it eat 357sig w/ no hickups? - MP-Pistol Forum

M&P40c, making it eat 357sig w/ no hickups?

This is a discussion on M&P40c, making it eat 357sig w/ no hickups? within the MP Reference forums, part of the Smith & Wesson MP Forum category; Has anyone on this site tried to make a M&P40 (Full size or compact) digest 357sig? The mags will feed both cartridges. The 357sig is ...


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Old October 23rd, 2010, 09:10 PM   #1
 
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Has anyone on this site tried to make a M&P40 (Full size or compact) digest 357sig?



The mags will feed both cartridges. The 357sig is really just a necked down 40S&W and should fit fine against the breech face and will work with the extractor in theory. The only issue is getting a barrel to fit correctly so as to allow the user to swap it when the whim hits him/her. So, has anyone here attempted it with positive or negative results? What went wrong if the attempt was negative. Any information would be great. I'd like to see if it would work...



Peace...
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Old October 24th, 2010, 05:44 AM   #2
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Quote:
Originally Posted by M&P45&40c' post='275959' date='Oct 24 2010, 12:10 AM
Has anyone on this site tried to make a M&P40 (Full size or compact) digest 357sig?



The mags will feed both cartridges. The 357sig is really just a necked down 40S&W and should fit fine against the breech face and will work with the extractor in theory. The only issue is getting a barrel to fit correctly so as to allow the user to swap it when the whim hits him/her. So, has anyone here attempted it with positive or negative results? What went wrong if the attempt was negative. Any information would be great. I'd like to see if it would work...



Peace...
You need a different barrel. Since the bullet is essentially a 9 mm (cartridge is necked-down .40 cal), you'll need a drop-in barrel to accomplish this. The .40 barrel is too big for the 9 mm projectile.



I have a .40 FS, but use the Storm Lake .357 SIG barrel and am very pleased. It's my carry configuration.
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Old October 24th, 2010, 08:49 AM   #3
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357 Sig cartridges will feed and fire in the 40S&W barrel but the case will no longer be reloadable. Also accuracy sucks.
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Old October 24th, 2010, 10:37 AM   #4
 
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Quote:
Originally Posted by M&P45&40c' post='275959' date='Oct 24 2010, 06:10 AM
Has anyone on this site tried to make a M&P40 (Full size or compact) digest 357sig?
As a search will show this is common switch barrel option. Generally speaking the pistol will operate interchangeably with factory .357 Sig and .40 S&W factory barrels although many and I'm one choose to buy the Storm Lake. Factory and Storm Lake barrels are readily available from all the usual suspects the sponsors above as well as Midway and Brownell's. Last time I looked Midway had a Storm Lake barrel in .357 Sig to fit the compact on sale. There are many such sales. Given a pistol that shppied in .357 Sig or in .40 S&W a conversion barrel (not the stock factory barrel) is usually required to do well with 9x19 cartridges and of course the 9x19 magazines. Storm Lake makes such a barrel. Rumor says one of these days Barsto will as well. Match barrels have been available in a few applications from David Bowie - does great work - and likely enough some others.



My own compact shipped in .40 S&W and I have Storm Lake barrels from Brownell's in .357 Sig and 9x19 - so far no hiccups in any configuration thought I don't doubt some combination of bullet and oal will cause hiccups - bullet selection in the .357 Sig is tricky for neck tension and ogive shape. I do use current follower design well sprung magazines as furnished by S&W for the 9x19 and for the .357 Sig/.40 S&W combination - YMMV.
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Old October 24th, 2010, 10:44 AM   #5
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Easy... swap in a factory .357 Sig barrel. Done.
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Old February 8th, 2012, 06:20 PM   #6
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Originally Posted by MichaelD View Post
Easy... swap in a factory .357 Sig barrel. Done.
my mp40/357 came with both barrells , it works just fine with either barrel.iwould just get a s&w 357 barrel,storm lake are very good barrells.,go to www.brownells.com,good luck. bophi
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Old March 1st, 2013, 10:11 PM   #7
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2nd Storm Lake
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Old June 29th, 2013, 04:39 PM   #8
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40 to 357SIG issue

I picked up a new factory S&W 357 SIG barrel for my 40FS recently and ran into issues. The 40 is accurate but the 357 SIG is shooting 3"-4" low & 1"-2" left, at 25'. The barrel seemed to fit fine & is functioning okay, except for accuracy. So far I've ran 3 types of ammo through it & all are low left.
If I was hitting high I think I could get it down with a little filing, but not sure what to do when hitting this far low. Since the original 40 barrel is "on" with the sights, I don't want to change them.
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Old June 29th, 2013, 05:06 PM   #9
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I shoot 357sigs through my FS .40 all the time (with a 357sig barrel of course) It is just as accurate, if not more than the .40. You know the little guy at the upper left corner of the targets, I shoot at those from 15 yds and the stock sights are dead on (for me anyway)
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Old June 30th, 2013, 04:44 AM   #10
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Originally Posted by FastDonzi View Post
I shoot 357sigs through my FS .40 all the time (with a 357sig barrel of course) It is just as accurate, if not more than the .40. You know the little guy at the upper left corner of the targets, I shoot at those from 15 yds and the stock sights are dead on (for me anyway)
Same here. I have a FS .40 S&W M&P and ordered the S&W .357 SIG barrel from Midway. My pistol shoots better groups with the .357 SIG barrel than with the .40 S&W barrel and that's the way I carry it. 124 grain HPs.
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Old June 30th, 2013, 06:51 AM   #11
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After reading how the S&W 357 SIG barrel is working okay for others I got out my bore sighter. At the same distance I was shooting, the bore sighter showed slightly low left, but nothing like I was getting while shooting the 357 SIG.
I think when I can wade through the mud I'll go back out back & make sure my mechanics are good. Shooting the FS40 fine as well as the compact 40, but maybe I'm focusing more on where the 357 impacts and not practicing proper trigger control.
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Old July 1st, 2013, 03:17 AM   #12
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It's not unusual for different loads of the same caliber to shoot to different points of impact. Different calibers can certainly shoot to different point of impact vs. another caliber.

You may end up needing adjustable rear sights for your gun. Or start looking for a .357 SIG slide and recoil spring/guide and just have a complete caliber change "upper".
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Old July 10th, 2013, 03:53 AM   #13
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I had the 357 factory barrel and never had an issue i used and abused it for about 6 months and 100% loved it, unfortunately i had to part with it. I couldn't find ammo for it and when i did the price gouge on already expensive ammo was too much. Maybe ill order another barrel from MidwayUSA or s&w because the shop i sold my barrel to is trying to get 110 for it when you can get a new one for 70... And i wont buy it back from them because hell give it to me for less but i know what he gave me for it so im not gonna let him make that much interest... The sig is beast!
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Old July 10th, 2013, 04:59 AM   #14
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It's hit or miss getting the 357 compact barrels directly from S&W. I got mine directly from S&W after my third try by just giving the part number and no mention of 357c barrel. If its at Midway, go for it. Storm Lake is another more costly but great option.

POA/POI is definitely different but accuracy is great either way. When I first got a 357 barrel, it gave me a sight picture like my Glock 19. Since I don't shoot the Glock anymore,I'm more comfortable shooting 40ís and the M&P40/40c sight picture.
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Old August 11th, 2013, 01:47 PM   #15
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I did it the other way. Had both full size and compact .357sig M&P's. Bought a Storm Lake barrel for the full size and a S&W compact barrel chambered in .40. Have had no issues with either. Makes a great trifecta to accompany the full size and compact 9mm. Now I also have a 9mm shield. Guess you could say I am an M&P believer.
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