.357 sig, .357 mag

R

ryanncass

Inactive
I'm buying a 357 mag. was wondering what is the difference between the .357 sig and the .357 mag.

Thanks for the info
Ryan
 
357Sig is a necked down .40Cal semi auto case. .357 is a rimmed revolver case

Here are both
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357mag is a long cased round designed for revolvers. The length of the case, and the fact that it's rimmed, makes it troublesome for reliable feeding in semi-autos.

357sig is a semi-auto round based on a 40 caliber case (not a 40S&W case, but 40 caliber) necked down to 357. It was designed to duplicate the performance of the 357mag in a semi-auto gun.

Depending on who you ask and which exact loading you are discussing it either does or does not match the 357mag performance. Most rounds do not, but the lighter ones are very close and some loadings do meet the 357mag performance levels, mainly loads from "specialty" makers like Buffalo Bore and Double Tap.
 
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The .357 sig was desingned to get .357 mag performance out of a semi-auto. But, it was only designed to get the same ballistic performance as a 125 gr .357 mag out of a 4" revolver. The .357 sig is a necked down .40 S&W casing with a 9mm bullet (roughly).
 
.357Sig is a short and rimless semi-auto pistol round. It's basically a necked-down .40S&W case loaded with a 9mm bullet. It has a rifle-style necked shape, unlike almost any other commonplace pistol round other than the 7.62x25 Tokarev.

The .357Sig is designed to duplicate the ballistics of a 125gr JHP .357Mag, which has achieved fame as a formidable manstopper. This was done to satisfy law-enforcement agencies, particularly state police forces, that wanted a semi-auto round with the penetrating power of a .357Mag that would still fit in a standard-size semi-auto pistol.

However, compared to a .357Mag, the .357Sig is IMHO somewhat of a one-trick pony- it duplicates the ballistics of a 125gr JHP load very well, but it's incapable of launching 158-200gr bullets like a .357Mag due to its restrictively small case. This is usually a deal-breaker if you intend to hunt large game with the gun, because those lightweight 125gr bullets won't penetrate adequately in a muscular game animal. You also can't fire "mouse phart" .38Spl wadcutter target loads in a .357Sig semi-auto pistol for practice.
 
Both have good power. Both are IMO the best cartridge for the job they were designed for. The biggest downfall of the sig is the lack of bullet choices. The sig is IMO the best auto round for LEO, CCW, and millitary. The mag is IMO the best revolver round for the same application. I just wish they would have made the sig a .357 instead of .355 diameter. I would love to see the abillity to load 158gr and 180gr sig rounds.
 
I would love to see the abillity to load 158gr and 180gr sig rounds.
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My understanding is that the case is simply too small to accomodate heavier bullets without creating an excess-pressure condition. In order to keep the pressure within limits, you would have to reduce the amount of powder so much that the load wouldn't approach the performance of a .357Mag cartridge loaded with the same bullet. This is why I describe the .357Sig as a one-trick pony. (Don't get me wrong, it does its one trick VERY well.) :)

IMHO the only somewhat commonplace semi-auto pistol round to equal the power and versatility of a .357Mag- high-velocity, flat-shooting, and capable of handling heavy bullets- is the 10mm Auto. However, it only fits in a handful of firearms, typically large and heavy ones, and its recoil is a handful; OTOH a .357Mag revolver can still shoot lightweight target loads. :)
 
I think you nailed it chris. Too bad, because i think it would have made a bigger splash and gained more followers if you could load heavy weights into that cartridge.
 
OK thank you I was at walmart and they were out of 357 mag but they did have 357 Sig. I dint want to buy Sig if they would not work Ill just look around some more for 357 mag.
 
OK thank you I was at walmart and they were out of 357 mag but they did have 357 Sig. I dint want to buy Sig if they would not work Ill just look around some more for 357 mag.
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yeah, not even close. It would be like putting a 9mm round in your 357 revolver.

I keep thinking about picking one up, but I've bought way too many guns in the last few months and I'd rather not get into yet one more caliber (that's not really a cheap one, either)
 
.357 mag

You can shoot .38 special in your .357 mag revolver. In fact I've seen really good accuracy in cowboy single action .357 revolvers with 38+ p ammo.
 
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think you nailed it chris. Too bad, because i think it would have made a bigger splash and gained more followers if you could load heavy weights into that cartridge.
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The cartridge was designed to approach the velocity of the .357M 125 gr. bullet that LE preferred. The only splash it was designed to make was with LE, and it suceeded. There was no other pretext, such as hunting, for the development of the cartridge.

From my Sig P229 both CorBon and Speer 125 gr. chrono at an honest 1400 fps. That exceeds some 4" .357' Mags. From my P226, the velocity is above 1450fps.

Federal 125 gr. JHP is 1375 from the P229.

One difference between the .357 and the Sig is that all .357 Sig bullets, except for CorBon, are designed to hold together and never seperate as required by LE.

It could be argued that if you wanted to duplicate the revolver performance, the CorBon would be the way to go, with jacket seperation or fragmentation being likely--along with the excellent stopping power that goes along with it.

I've always found it amusing that some of the strongest believers in 357 mag. "stopping power" are the strongest advocates for semi-auto bullets that never shed their jackets---or, God forbid, fragment.
 
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My HK USPc in 357sig liked the hornady 147gr xtp's. That was also the heaviest round i found for it. I love the hornady's but they were a bit underloaded. I think handloading this cartridge i would use the xtp's in 147gr and try to find a hotter load than the Hornady factory stuff.
 
Bullet weights, diameters and SD

are a few differences.

As noted, the .357 Sig is a .40 S&W necked down to accept 9mm (.355) auto bullets. Out of a 4-5" auto the hottest 125 grain bullets in the Sig are almost as fast as the .357 Magnum's out of a 4-5" wheelgun, but the .357 uses .357 caliber bullets, usually with cannulars for roll-crimping as opposed to the taper of the Sig.

The .357 Magnum out of a modern wheelgun can generate much higher power levels with bullets greater than 125 grains, however. Try pushing 200 grain hardcast bullets out of your Sig at 1350 fps :) No, don't!

The Sig is really more like a 9mm +p+/subgun load or .38 Super+p but with better feeding characteristics.

It is a good SD round, but not in the same league as the .357 Magnum when both are loaded to full potential. You do, however, get more shots from a bottom feeder.

Cheers

Funon1
 
It is a good SD round, but not in the same league as the .357 Magnum when both are loaded to full potential. You do, however, get more shots from a bottom feeder.
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I'd say it's better than a good SD round with street data that supports that statement. A round that comes close to .357 Mag. with close to 9mm mag. capacity, built on a 9mm frame, was the whole idea. And, as stated, 1400 from my P229 short barreled pistol exceeds some revolver rds. fired from a 4" revolver.

A six inch revolver will exceed the Sig levels, and most 4" revolvers as well. A P226/.357S flirts will real .357 Mag. territory.

I wouldn't exactly feel inadequately armed with CorBon's 115 gr. JHP at 1500 from the P229, either (not sure if they still produce it).

No 147 gr. or heavier bullet is going to perform as well as a 125 gr. bullet for SD in the Sig round.
 
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As noted, the .357 Sig is a .40 S&W necked down to accept 9mm
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Well, kinda sort of..... but actually, its not. The 357SIG case, while similar to a necked down .40S&W, it is its own specifically designed case.

If you neck down a .40S&W, which can easily happen if your not paying attention, the case will be too short. The .40S&W brass is also not as heavy as the 357SIG brass, which was designed to handle the higher pressures generated by the 357SIG.
 
The .357 Magnum is a revolver round that was developed in the 1930's. It was an evolution of the .38/44 which was itself a .38 Special loaded to higher pressures. Out of concern for this ammunition being loaded in older guns, it was decided to lengthen the cartridge case, thusly allowing it to be loaded to even higher pressures and preventing it from fitting in a standard .38 Special cylinder. Original ballistics for the cartridge boasted a 158grn bullet at 1500fps from a 8 3/4" revolver barrel. As currently loaded, typical ballistics include a 158grn bullet at 1200-1250fps and a 125grn bullet at 1400-1450fps with both velocities being measured from 4" revolver barrels.

The .357 Sig was developed in the 1990's in an attempt to get the performance of the 125grn .357 Magnum in a semi-automatic handgun. This was basically accomplished by bottlenecking the .40S&W down to 9mm thusly allowing a larger powder capacity and thusly higher velocities. As originally loaded, it featured a 125grn bullet at 1400-1450fps from a 4" semi-automatic barrel but most manufacturers have reduced their velocities to approximately 1350fps (the cartridge is still loaded to it's original velocities by Cor-Bon, Buffalo Bore, and Double Tap).

While the .357 Sig is undoubtedly a good cartridge, it is still unable to attain the power or versatility of the .357 Magnum. While the Sig, in it's top-end loadings, can match the ballistics of typical 125grn .357 Magnum loads, it must be remembered that such loads are not top-end .357 Magnums. Top end Magnum loads from Double Tap and Buffalo Bore can achieve velocities in excess of 1600fps with 125grn bullets from 4" revolvers. Likewise, the .357 Magnum is available in a much wider range of bullet weights ranging commonly from 110grn-180grn and even a few 200grn loadings while the .357 Sig is loaded commonly only with 125grn bullets with just a few 115grn and 147grn loadings.
 
What many seem to leave out in the comparisons is, with the autos shooting the 357SIG, you usually get a high cap gun, that is much easier to shoot well with over the revolvers. This is especially true of the smaller autos that are basically crowding into the J frame revolver range.

You also dont get the muzzle blast and flash out of the 357SIG's (basically none of either) compared to the 357MAG, and again, especially with the smaller revolvers.

While I agree that the 357MAG can be more versatile (especially out of guns with longer barrels) across a broader range of uses, when it comes to the main reason for the 357SIG, the round it duplicates is the round that was most carried for the same purpose in the 357MAG's, a 125 grain JHP running around 1450fps out of a 4" barreled gun. If the 357MAG were still as viable a weapon as some seem to claim, especially since you can load it up so much hotter, I wonder why it is you dont see more people carrying 4" and 6" Model 19's, 686's, 620's, and 27's/28's, etc, instead of high cap Glocks and SIG's in 357SIG?

I know the reason my 357MAG's have mostly been setting in the safe for the past 15+ years. They are bulky, carry half or less what most of my equivalent powered autos carry on board, and take more work to stay on top of, especially if you practice with realistic ammo. My P239 or P229 in 357SIG, will shoot groups at 15 yards I struggle to shoot with my 60 at 7 yards, and I can shoot the P239 or P229 all day long with full powered loads in practice if I want. The 60, I'm lucky to get through a box of 50 factory level loads before my hand (and my targets) tells me to stop.
 
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