View Full Version : Sig 229 .40/.357 Sig mag question

06-30-2005, 5:16 PM
I am thinking of getting a Sig 229 in .40SW and a conversion barrel for .357. The mags are interchangeable, but from what I've read 10 round .40 mags can fit one or two more .357 rounds. What are the legalities concerning these mags? Do I have to get the 10 round .357 mags and not fit 10 .40 rounds or do I have to buy 10 rounders for each and switch every time I switch barrels? Thanks in advance.

06-30-2005, 5:57 PM

Not true!!

357Sig is really just a necked down 40S&W: the 40S&W and 357Sig rounds have the same case head and rear of case diameter - it's just that the 357Sig has its front end necked down for narrower bullet. Thus you will only be able to fit 10rds of 357Sig in there as well. The 357Sig and 40S&W mags are identical and are not differentiated.

The Sig 229 is also available in 9mm, but beside a different barrel and magazines, it would (99% likely) use a different slide. Recoil spring'd likely be different too.

[Someone may have managed to get some kinda 9mm conversion bbl (_not_ a Sig) running but the breech face & extractor on slide would be just wrong and it'd be lucky to run. However the 40S&W/357Sig mag might hold an extra 2 rounds of 9mm - not sure it'd feed right at all, etc. This has apparently been done on the Sig P2340 polymer gun.]

Legally, I believe inappropriate use of a 10rd magazine (wrong caliber) to get higher capacity could be construed, possibly, as constructing an illegal hicap mag.

Anyhow, bottom line: if you have a P229 in 40 or 357, the 10 round mags are the same for each of these 2 calibers and will only hold 10 rounds.

Bill Wiese
San Jose

06-30-2005, 6:23 PM
Bill, thank you for clearing that up for me; now I have no worries. http://calguns.net/groupee_common/emoticons/icon_smile.gif

07-08-2005, 4:50 AM
my 229/40, on the mags,. it says ".40/.357" on the side...

barsto makes the 9mm barrels. and i heard that 228 mags MAY work with 10 9mm rounds...

if you can, get the .357 version first and then get the .40 barrel next. sometimes i see .40 barrels under $100 and the .357 ones over $150...

07-08-2005, 6:25 PM

I can tell you from personal experience that a sig 229 in 40s&w can be converted to 9mm with only a special conversion barrel and a sig 228/229 9mm magazine. I'm not sure this will work in all 40 cal pistols but it does work with sigs quite well.

While one could get an extra round or two of 9mm in a 40 cal mag, it is not recommended due to feed problems.