Sig P239 40cal to 357 Sig

This is a discussion on Sig P239 40cal to 357 Sig within the Defensive Carry Guns forums, part of the Defensive Carry Discussions category; I've just ordered a CPO Sig P239 in 40 cal, with the intention of shipping straight back to the Sig custom shop for an SRT, ...

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Thread: Sig P239 40cal to 357 Sig

  1. #1
    Member Array Flfiremedic's Avatar
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    Sig P239 40cal to 357 Sig

    I've just ordered a CPO Sig P239 in 40 cal, with the intention of shipping straight back to the Sig custom shop for an SRT, and hand fitting of the 357 Sig barrel. It will be an edc. Do I need to have it re-sighted for 357? I've heard stories of different POIs, so was thinking of having it re-sighted with 25 yard zero in new cal. Will this be an added expense, and will it be necessary? I am not sure how the change in POI is accomplished. Any input would be appreciated.
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    Senior Member Array sensei2's Avatar
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    my first P-229 (1994-5) was factory chambered in .357SIG. i later bought a factory Sig .40S&W barrel for it. no fitting was necessary. i think POI is about the same, but i rarely shoot .40. the barrel is mostly insurance in case .357SIG declines as a caliber.

    my second P-229, an Elite Dark (about 2009), was bought in .40, and i bought a factory Sig .357SIG barrel for it. again, no fitting was necessary. and again, i believe that POI is about the same, regardless of caliber. in any case the Elite has adjustable rear sights, so i can easily shift the POI if i have to.

    in a gun with fixed sights, POI is moved by shifting the rear sight left or right (to make lateral adjustments), or by replacing the front sight with a taller or shorter one (to make vertical adjustments).

    changing bullet weights can also shift POI. generally, lighter, faster bullets will impact lower, because they leave the barrel quicker, before the muzzle has had as much time to rise. heavier bullets generally impact higher for the opposite reason. in .357SIG, your choices of bullet weight are most commonly 125 grain or 147 grain. i only shoot 125 grain in .357SIG, and i generally use lighter (135-165 grain) bullets in .40.

    perhaps the simplest thing for you to do is to have the factory install an adjustable rear sight in your gun, that way you can adjust the POI to YOUR sight picture. POI can vary among individuals. two people shooting the same gun might have different POI, which is why i recommend adjustable sights for you. good luck.

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    Senior Member Array patri0t's Avatar
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    I have had .357Sig & .40S&W, both as LE issue sidearms.
    I would think any difference in POI at 25 yards could be adjusted for in bullet weight. At reasonable SD ranges, the difference would certainly be negligible.

    My idea would be to see how it works with a simple bore sight and if the POI is significantly different, I would jump on some custom night sights in a 'perfect' config to suit my style of shooting.
    Too nice of a sidearm to be stuck with factory sights. How not to love a .357Sig!! Nice choice.
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    Distinguished Member Array matthew03's Avatar
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    Sig uses two different front sight heights between their guns chambered in .357 Sig and .40 S&W. A factory Sig Bbl. should not need to be fitted by a gunsmith/armorer in a .40 caliber gun.
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    VIP Member Array 357and40's Avatar
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    MY S&W M&P40c (and 357 sig barrel) and my Sig P229 40 (and 357 sig barrel) do not really have a different PoI at close range. Longer distances the 40 will drop faster than the 357, but if you are concerned about it for defensive purposes at defensive distances, it is not going to be worth the concern.
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    VIP Member Array Kennydale's Avatar
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    Help a newbie out.
    the Sig.357 will load into the .40 magazine? just need a barrel conversion ?

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    Senior Member Array sensei2's Avatar
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    Quote Originally Posted by Kennydale View Post
    Help a newbie out.
    the Sig.357 will load into the .40 magazine? just need a barrel conversion ?

    My Sig P-229 magazines are marked for both calibers. i know that Glock makes separate magazines for their .40's and their .357's, but i don't know if they are interchangeable. i don't know about the S&W M&P guns/magazines.

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    Member Array zeke4351's Avatar
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    I have a Sig P239 in .40 and I bought a .357 Sig barrel and it fits fine. The P239 magazines are not marked for .40 and .357 like other model Sigs. I have read that the .357 would work in the .40 magazine but not the other way around. I found some new .357Sig factory magazines cheap at Topgun Supply and I bought 2. Comparing the mags side by side there is a big difference between the .357 and .40 so I am glad I ordered the .357 mags . For EDC I wouldn't want to chance using the .40 mags and .357 barrel. I also have a P229 .357 Sig and a .40 barrel for it. From my experience I would not worry about changing the sights for each caliber. I don't have the SRT trigger but have read where some experienced shooters are afraid to use them in their carry gun for fear of shooting a second or third time not aiming to. It seems they wouldn't trust the safety of it in a stressful situation. Thought you might want to do some research before spending the extra money.

  10. #9
    Member Array Flfiremedic's Avatar
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    I appreciate the input...a lot of good advice here.
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