So my quandary is this. I have a P229 in .40 and numerous Sig 229 mags. The mags marked .357/.40 are too thin in the neck to allow the upward indexing of .40 rounds. The mags marked .40/.357 allow the upward indexing and feeding of .40 just fine. Am I correct in my presumption that the mags marked with the .357 designation first are designed for .357 and not for the .40 ? Why the confusing labeling if this is the case ? Thanks for any help you can offer.

I am sure someone more well versed then I will chime in but I will take a stab.

AFAIK the P229 mags were completely interchangeable between .40/.357. The only mags SIG made that were proprietary in this regard were for the P239 and even those more or less worked one way or the other for both.

The P229 however did go through a change at some point where the newer mag well was either thicker or thinner and the mags were changed in some way. I don’t know the specifics off hand. Point is could you be using to different generations of mags?

Chris

Hmmm, I have a p229 in .357 and a 0.40 barrel as well.

I've never had any feeding problems using the same mag for either caliber.

Perhaps someone has other advice?

I have a Legion P229 .357 sig so it could only apply to newer ones but I have a few of the older zipper back mags and they work with both .40 and .357 sig barrels.

I’m not sure I understand everything about the question, for example what the “neck” of a magazine is.

In any event, my first SIG (in 1994) was a P229 chambered for 40 S&W, and not long after the 357 SIG cartridge was introduced I purchased my first barrel chambered for that round. Since then I’ve fired more 357 than 40 with my P229s, but a fair amount of the latter. I have also always had a keen interest in both the pistol and the two cartridges. This is literally the first time I’ve ever seen anyone question the differences in 357/40 magazines. Some early ones are just marked 40, some were (evidently) made in Germany (the ones with dovetailed seams), and some made in Italy. Perhaps some of the most recent ones were made in the US, but I have no actual knowledge of that.

I am curious whether the issue being questioned in the original post is based on measurements and observations of how the cartridges sit in the various magazines, or whether actual malfunctions have regularly occurred with using 40 S&W ammunition in magazines with 357 as the first marking. There may be differences among various mags, but do they have any effect on actual functioning? The 40 S&W cartridge has always been far more popular than 357 SIG, so if some magazines were not reliable with 40 ammunition, I cannot imagine that it would not have been widely reported, including on this forum. It hasn’t. Ever. In the nearly 19 years I’ve been a member here.

In fact, one of the things I’ve remarked about over the years is how the P229 chambered for 357 SIG or 40 S&W has probably been the most trouble-free of all the Classic line SIG pistols based on what I’ve seen posted here.

I have many 357/40 P229 magazines, most of which I’ve never used, and without more effort than I’m willing to exert at the moment, I don’t know if I have any that put the 357 marking before the 40. I am therefore curious about the 357-first mags: Where were they made? Are they factory mags? Anything else of interest?

Unless something has changed, the .40 and .357 229 magazines are exactly the same and are marked for both calibers. All my duty mags are so marked and all my personally purchased magazines are as well. They also feed both calibers without issue.

My good mags are marked .40 / .357. My mags that wont feed .40SW are marked backwards. They are .357 / .40. There is also a slightly different geometry in where the mag narrows up towards the feed lips (neck). I'm just going to presume I got some mags from Checkmate/Promag and relegate them to range use only. There is no country of origin stamped on them like the good mags so...I presume I have a couple of crap made mags.

If they are off brand mags that is likely your problem.

SIG factory
MEC-Gar (who make SIG factory mags)
Checkmate (Who either are currently or supplement factory mag production)

Any of those should be good to go.

PRoMag is the most commonly seen aftermarket mag and they are......well they make great door stops, ornaments, immediate action trainers, interesting candles......pretty much anything but a reliable magazine. . So if they are Promags.....well “There’s yer’ problem.”

I thank ya folks. Life's too short for crap mags.

Isn’t the .357 Sig round just a necked-down .40 case seating a 9mm bullet? If so, then they should both cycle equally well through magazines designed for either/both, since from what I’ve observed, the lips only cover the case about halfway up from the base of the round. I do have a .357 Sig barrel that I’ve never fired (I don’t even ave any .357 Sig ammo) so I may talking out of my ass...

quote:

Originally posted by SigFan:
Isn’t the .357 Sig round just a necked-down .40 case seating a 9mm bullet?

Yes, it is, but because the 357 bullet and case neck are smaller in diameter than the 40’s, it’s conceivable that it would chamber properly if misaligned with the barrel to a greater degree than would work with the 40. I.e., a magazine manufacturer could be more careless in designing and manufacturing a magazine intended for use with 357 SIG ammunition than could be gotten away with for a mag designed for the 40 S&W. More reliable chambering was a fact that the pundits regularly mentioned back when the 357 cartridge was first introduced.

quote:

Originally posted by sigfreund:

quote:

Originally posted by SigFan:
Isn’t the .357 Sig round just a necked-down .40 case seating a 9mm bullet?

Yes, it is, but because the 357 bullet and case neck are smaller in diameter than the 40’s, it’s conceivable that it would chamber properly if misaligned with the barrel to a greater degree than would work with the 40. I.e., a magazine manufacturer could be more careless in designing and manufacturing a magazine intended for use with 357 SIG ammunition than could be gotten away with for a mag designed for the 40 S&W. More reliable chambering was a fact that the pundits regularly mentioned back when the 357 cartridge was first introduced.

Roger that!

Checkmate P229 mags are suspect. I purchased a P229 SSE that came with Checkmate mags that had issues. Stick to the MecGar mags and you should be fine.

Some Mec-Gar mags are not marked with their name but only say Made in Italy.