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Could i just use the .40SW mags for the .357?

or does SA make mags for the .357? also is there any mags out there that hold more then 12rds for the .357 ?
 

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.40 S&W mags work for the .357 SIG also. Yes SA does make actual .357 SIG mags.....well, actually its the same mag as the .40 with a baseplate that says .357 SIG on it.

More rounds than 12....havent seen any really. Even if I did I probably wouldnt trust it to function right unless it came from SA.
 

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Press damn hard and I mean break your finger while using a mag loader hard and you can squeeze 13 in some of the 40 mags but its one hell of a fit. Every 40 mag I've been able to do that to and not even realize it. I helped load a buddy's 40 mags and the side view holes that show round count doesn't line up 100% with 40cal casings so what I thought was 12 was actually 13.

XD-Ro is completely right about the 40/357 sig mags being the same but different faceplate. Afterall, 357 sig is just a 40 cartridge necked down to .354
 

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XD-Ro,

As previously posted, yes, the .40 magazines work for the 357 Sig XD. Half my magazines for my .357 XD are labeled as .40's and half are 357 Sig.

ampleworks,

Actually, the 357 Sig isn't the .40 S&W necked down, even though it looks like it. The 357 Sig case is thicker in both the web and at the base, just above the web, to withstand the higher pressures of the 357 Sig round. If you simply neck down .40 S&W brass, the case comes out considerably shorter than the Sig round, leaving a very short neck and a case that is dangerously overstressed when loaded to full power 357 Sig specifications.

There is some speculation that the 357 Sig was actually a derivative of the 9x25 Dillon, which is the 10mm case necked down to 9mm. There was some interaction between Dillon and Sig prior to the introduction of the 357 Sig cartridge, and a Sig representative took some samples of the 9x25 back to Sig about a year before the round was announced. There is the difference of the primer pocket sizes between the 357 Sig and 9x25, but basically, the 357 Sig round more closely resembles the 10mm case than it does the .40 S&W, other than the different primers used. This information was given to me by a former Dillon employee who worked on the 9x25 project.

XD-Ro,

If you really need more than 12 rounds for the 357 Sig (or for that matter, the .40 S&W) in the XD, there is a way to do it. As an experiment, I used a Pearce +2 grip extension and the spring and follower from a LEO marked .40 magazine and I was able to get 15 rounds of 357 Sig ammunition into it. The springs and followers are different in the LEO magazines and the 10 round post ban magazines. With the post ban follower and spring, I was only able to put 2 more rounds into the magazine.

As a side note on springs, the 10 round 9mm Compact magazine spring is about five coils longer than the full size 10 round 9mm magazine spring. Evidently, this was one of the means that was used to restrict the compact magazine to 10 rounds. They simply made the "spring stack" longer, so the follower couldn't go deeper into the magazine.

Hope this helps.

Fred
 

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synchro,

The LEO magazine followers have a thick center post, which the spring fits around, while the post ban 10 round magazine followers have four legs, one at each corner of the follower, very similar to the S&W Model 59 magazines. The center post of the LEO follower is shorter than the legs of the post ban follower, which allows it to go down farther. The LEO spring is also wound narrower at the top, and widens out part way down, which affects the spring stack, making the stack shorter, thereby allowing more rounds in the same length magazine. There is also a difference in the magazine base pads between the two.

It's easier to see the difference than it is to explain it. If you get a chance to compare the two magazines side by side, disassembled, it's easy to see the differences. There are also no dimples in the LEO and hi-cap magazine bodies to restrict the follower travel.

Hope this helps. (and makes sense)

Fred
 

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Thanks ReloaderFred, that's a lot of good information. I'm going to take apart my postban mags tomorrow to see what you're describing. I'm wondering if shortening the postban follower legs would be feasible, and allow an extra round. :?:
 

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willbond,

Shortening the legs alone probably won't do much. You'll probably have to get rid of the dimples, too. The spring stack also comes into play. Be sure to leave enough of the legs to keep the follower straight in the magazine body. That was a problem with the early Model 59 magazine followers, and S&W solved it with the longer legs on the later followers. They did upgrades on existing magazines in the late 70's for free.

Hope this helps.

Fred
 

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Actually, the 357 Sig isn't the .40 S&W necked down, even though it looks like it. The 357 Sig case is thicker in both the web and at the base, just above the web, to withstand the higher pressures of the 357 Sig round. If you simply neck down .40 S&W brass, the case comes out considerably shorter than the Sig round, leaving a very short neck and a case that is dangerously overstressed when loaded to full power 357 Sig specifications.
Stressed? Yes
Does it work? Yes
Did you take what I said and take it out of context? Yes

The casings are the same physical diameter...perhaps not thickness but does it really matter? We're talking magazine size. The 40 is .020" shorter.
 

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ampleworks,

My comments were only meant to clear up what may have resulted in some confusion for the uninformed. The two cases are not identical, as we both know. If someone took what you posted literally, and placed sized down .40 S&W cases in an unsupported chamber, with full loads meant for the 357 Sig, then there is a very good possibility of the case blowing out at the web and damaging both the shooter and the firearm.

My clarification was not meant to demean you in any way, and if you took it that way, I apologize.

I just believe that since we're dealing with some very high pressure cartridges, that we must be clear on our meanings.

Hope this helps.

Fred
 

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Yeah I get what your sayin, sorry for biting back :x

We're talking an extra 5,000 PSI or so if loaded within SAMMI specs about 2gr extra charge over a 40. Lighter loads would work in a 40 casing just fine. Heck, if anyone went and reloaded casings by just a single forum post....maybe they need a lesson in stupidity.

I forgot which reloading manual it was...either Lee or RCBS, but it specifically states that you can load 357 sig in a 40 but never mentions using it for light loads or unsupported chambers.
 
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