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.40-to-9 Conversion and .357SIG Question

Discussion in 'General Glocking' started by FLAHOTROD, Nov 6, 2012.



    Sep 18, 2008
    Gainesville, FL
    Good evening and Happy Election Day! I hope it proves to be a good outcome for the gun community.

    I apologize a thousand times over if this is a question that has been asked to death, but I am not lazy. I did a forum search and did not find these questions posted earlier. If I missed them, then shame on me.

    I have a Gen4 G22 and a Gen1 G27. I would like to add a Gen4 G23 to round out the .40 collection. I am intrigued by conversion barrels that will allow me to convert these into 9mm's. I fully plan to use 9mm magazines when using the conversion barrels. Here are my questions:

    Will I need to buy different guide rods and recoil springs for the Gen4's? If so, do they need to be specifically designed for the conversion, or will Gen3 9mm guide rods and springs work?

    Since the .357SIG is essentially a 9mm projectile in a necked down .40 case, will a combination of a .40-to-9 conversion barrel and a .40 magazine allow me to shoot .357SIG or are there other factors that keep this from happening?

    Thanks in advance for your replies. :winkie:
  2. plouffedaddy


    Apr 1, 2011
    I'm not aware of the existance of any Gen1 G27s.

    Yes, the cutouts are different. Theoretically you'd need different springs in the Gen4s for optimum reliability but it would probably work fine with the stock 23 spring.
    No, the chambers are different.

  3. Giggity-Giggity

    Giggity-Giggity Giggity-Goo!!!

    Feb 2, 2007
    Gun Tot'n in Quohog
    I got a Lone Wolf 40-9 for my Gen3 G35 and had a lot of failure to extracts and Lone Wolf requires just a 9mm magazine. Sold off the 40-9 conversion barrel and got a Gen4 G17. I'm NEVER touching another conversion barrel ever, but for this...
  4. MikeNH


    Jul 18, 2009
    You'd just need a 357 barrel to shoot 357. Mags too probably but some people do use .40 mags. I have a 9mm conversion in my G32 (357) and 9mm mags and zero malfunctions.
  5. abq87120


    Nov 2, 2007
    Prescott, AZ
    I have LWD 40-9 conversion and 357 Sig barrels for my Gen3 G23. Except for 9mm mags for the 40-9 barrel, no other mods. All three barrels are sweet shooters.


    Sep 18, 2008
    Gainesville, FL
    My mistake. Poor choice of words. What I meant to say is that it is an early version, about 15 years old. I'm not sure if there is a "generation" for the G27s.

    Thanks, everyone, for the comments. I appreciate it.

    Is there a .357SIG conversion barrel for any of my .40 models? I seem to only see 9mm conversion barrels listed or mentioned.
    Last edited: Nov 6, 2012
  7. ADK_40GLKr

    ADK_40GLKr Adirondacker with a Glock

    Nov 14, 2010
    RFD NY Adks
    As I understand it, you only need an original Glock .357 Sig barrel as the barrel diameter is the same as a .40 barrel. They say .40 mags work fine with .357 Sig ammo.

    This should help you ID your Generation:

    This thread tells a bit about the history of when each model was introduced as well as serial number dates:
  8. SJ 40

    SJ 40

    Jan 17, 2011
  9. ...Gen 3 GLOCK 23 here...I never shoot it as a .40 S&W...

    ...Picked up a Storm Lake .40/9mm conversion barrel and 3 G19 magazines...100% reliability with just these two changes and 124GR Speer Gold Dot or Speer Lawman...have carried for self defense and trust it all the way...

    ...tried out a GLOCK 32, 357 SiG barrel and my G23 .40 S&W magazines (LE/Gov't marked)...100% but it seemed at times that the slide was having some issues but no failures to go into full battery...I picked up two newest vintage GLOCK 357 SiG magazines with the newest 357 SiG followers (higher peak than those I have for the G23) and they work perfect for me...

  10. Bruce M

    Bruce M

    Jan 3, 2010
    S FL
    This might help to picture the relationship between .40 and .357 Sig. The same at the base but necked down at the top.



    Sep 18, 2008
    Gainesville, FL
    ^ That's why I was hoping that the .357SIG would work with the 9mm conversion barrel and the .40 magazine.

    Thanks for all the replies, gentlemen. I do appreciate you sharing your time and expertise with me.
  12. 2-8 Marine

    2-8 Marine Limp Member

    Oct 30, 2009
    I'm no expert and I can only provide my own experiences with my G27 (3rd gen) and conversion barrels. I purchased a lone wolf conversion barrel in 9mm and one in .357 sig and they both work perfectly. I use my G26's 9mm mags with the 9mm barrel and my G27s .40 mags with the .357 sig barrel and have experienced no faliures to feed or failures to eject. I've heard this is not always the case but so far, so good. Hope this helps.
  13. 2-8 Marine

    2-8 Marine Limp Member

    Oct 30, 2009
    I'm pretty sure .357 sig WILL NOT WORK with a 9mm conversion barrel.
    A .357 sig conversion barrel WILL WORK with .40 mags though.
  14. SCmasterblaster

    SCmasterblaster Millennium Member

    Sep 24, 1999
    Hartford, Vermont
    Nice pic!
  15. Valerko


    Jun 17, 2012
    You don't even need 9mm mags.
    I have G35 with LW 40-9 conversion barrel. That's the only thing I change ,40 mag will feed 9 mm just fine. Only thing different when shooting 9mm is the way casings eject. They go 12-1 o'clock ,instead 2-3 o'clock like .40.
  16. SCmasterblaster

    SCmasterblaster Millennium Member

    Sep 24, 1999
    Hartford, Vermont
    BTF? Oh no!
  17. Poohgyrr

    Poohgyrr trout fear me!

    To shoot 357 Sig from your Glocks, buy the Glock factory barrels in 357Sig: A G31 barrel for your G22; a G33 barrel for your G27; and if you buy a G23, then buy a G32 barrel. This ability is one of the advantages of buying a Glock, if Glocks work for you.

    Similar to the way we can shoot 38 S&W Specials and 357 Magnums from a good 357 Magnum revolver. Same for other revolvers in the 44 and 45 Magnums.
  18. Everything works just as it's supposed to... no FTF... no FTE...

    Last edited: Nov 7, 2012


    Sep 18, 2008
    Gainesville, FL
    Thanks for all of the replies, along with your helpful information, recommendations and suggestions. :supergrin:
  20. This thread confuses me, and I own a conversion barrel. Just for clarity sake (for the OP...if you understand this then ignore me):

    If you own a 27 you must buy a 40-9 conversion barrel. I love my Storm Lake one. You can only shoot 9mm through this barrel and only with 9mm mags. No other adjustments necessary.

    You may not shoot .357 through a .40-9 barrel or a .40 barrel. You may shoot .357 through a factory g33 barrel, which should fit in your 27 without issue. You do not need to change internals, and it is debatable whether you need to buy .357 mags (though the predominant opinion I have seen is that you do NOT need .357 mags).

    Sorry, I'm a teacher and I just wanted the directions to be clear. :whistling: :supergrin:
    Last edited: Nov 9, 2012