.357 or .357

In past years, various writing projects have caused me to research a couple of cartridges with similar sounding names—the .357 Mag. and the .357 Sig. Trying to match the two is like comparing apples and oranges. It can be done, but doing so produces rather little in the way of really meaningful data. Nonetheless, let's take a look.

The .357 Mag. is a wonderful cartridge introduced in 1935 as the first really high-velocity revolver cartridge. It is a remarkably versatile round and any gun chambered for it will also fire .38 Spl. loads, so it is really a gun that provides a big part of the versatile tab. But it is also true that the .357 Mag. cartridge is available in loadings with bullets running from 95 to 180 grains. That gives this vintage cartridge amazing versatility. Literally, you can find loads that deliver short range, low recoil speedsters of around 100 grains at zippy speeds and others that use heavier bullets (sometimes close to 200 grains) at a little more sedate velocities. Depending on personal preferences on how to best approach the shooting job at hand, a .357 Mag. gunner has many choices.

Not so with the .357 Sig. This auto pistol cartridge is essentially a .40 S&W necked down to take a .355-inch bullet. The case is reminiscent of the .30 Luger, except for a larger size, if not length. Intended for 9 mm sized pistols like the Sig P229, the cartridge is available with a smaller variety of bullet weights than the .357 Mag. Bob Forker's excellent book “Ammo & Ballistics 4” lists a few loads with 115-grain and lighter bullets, as well as a few with 140 and heavier. But the near universal choice for this round is a 125-grain JHP bullet. I have had a considerable amount of shooting experience with this type of ammo in a couple of different pistols. The greatest strength of the concept is functional reliability—the small bullet feeding into a large chamber just plain works. You can't really compare the two in the broad sense, but as a personal defense round, there is some logic in a shootout.  

Police agencies once used the Magnum extensively and most commonly issued 125-grain ammo for it. Although the 125s were not the only police .357 loads, they were the most popular. Several police departments now use .357 Sig pistols, and the 125-grain JHP load is popular.  In this sense—Magnum versus Sig—a comparison is in order, but only if you limit the field to that single bullet weight. I once did this and the results were startling. I used a selection of typical loads in the 125-grain bullet weight in both calibers, and the guns involved were of comparable barrel length—a 4-inch S&W revolver against a 4.2-inch Sig pistol. There were eight different loads in each caliber, and I fired ten rounds of each through the appropriate guns, chronographing with an Oehler Model 35P chronograph.

While the fastest single load—a red-hot 125-grain JHP—was a .357 Mag., the average velocity of all .357 Mag. loads was 1,270 fps. The average velocity for eight different .357 Sig loads was 1,350 fps. Although I have been accused of all manner of skullduggery in publishing these results, the fact remains that the Sig outruns the Magnum. It is also notably easier to shoot, with less felt recoil and much less muzzle blast. As pistol cartridges go, the Sig functions very reliably and appears to be easy on the gun. Finally, I can't leave the subject without mentioning the obvious. A fully loaded .357 revolver offers six or seven rounds on tap and a fully loaded .357 pistol gives you up to seventeen rounds (depending on model). 

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7 Responses to .357 or .357

Harry wrote:
April 19, 2014

Don't fool yourself 1250 fps with a 158 grain bullet out of a 4'357 magnum revolver is a mild load. most 357 magnum ammo is loaded mild because of all the tiny 5 shot revolvers in use. Some of these revolvers aren't even made of steel and shooting full power loads out of them would be painful. You also have to worry about bullet setback. The original 357 magnum load was a 158 grain semi wadcutter doing 1550 fps out of an 8 3/8' barrel and you can still achieve this performance today with handloads. The 357 Sig is a nice round, but a 357 Magnum in a different league.

me wrote:
February 18, 2013

Part of the problem here is that the max pressure for the .357 Magnum has been reduced by a third or more over the years. As developed by Elmer Keith, for Smith N-frame revolvers and the Colt SAA, pressures ran close to 50,000 CUP, using the old copper crusher method which produced measurements only approximately equal to PSI. SAAMI reduced the max pressure specs to 45,000 CUP in 1980, then in 2005 cut them back further to 35,000 PSI. Given that NATO-spec 9mm ammo has a max pressure of 42,000 PSI, and typically stays very close to that due to the military requirement need to keep open-bolt SMGs running under adverse conditions, we as a result have the strange situation where military-spec 9mm pistol ammo with a 124gr bullet runs at 1200-1250 f.p.s., and the .357 Magnum beats that by less than 100 f.p.s. with 125gr bullets. I would recommend that Mr. Clapp, should he be interested in the real difference in ballistic potential between the two rounds, consider handloading some .357 Magnum using 125gr jacketed hollowpoints over 22.0gr of H110/W296, or working up to 19.5gr of H2400 (tested and shown within safe limits at 46,000 CUP in Speer Reloading Manual #10, 1979), and tell us how fast the chrono says they run out of a 4" revolver. I hasten to add that these are the real thing, full tilt boogie .357 Mag loads going balls to the wall, and I would not shoot them in anything smaller than an L-frame or a GP100 if I were you, nor any revolver with a frame made of anything but steel. And while you're at it, try loading some 158gr or 180gr bullets in the 357 SIG and tell us how that works out for you. The only way it looks like there can be any comparison between the wheelgun cartridge and the weird little bottleneck semiauto cartridge is if you use watered-down ammo and watered-down load data for the former. There is really no comparison between them.

attention to detail wrote:
May 01, 2012

well,my name failed me here gary!they are 148grain and 142 grain not 158!(should have read box)lol,they are fiocci and buffalo bore loads commin out of a ruger gp 100 w/a six inch barrel.and unless the ranges chrono is wrong(possibility)they all were above the 1400 fps mark!the buffalo bore 158 was averaging 1436,fiocci 142 were 1429,and the fiocci 148 were 1412fps i swear to u!now most folk wont use buffalo bore in thier pistol(the ruger gp100 loves em,great for pig thumpin)the fiocci's are a common round used from factory!check them out sometime.they are hot!all this being said,i apologize for any confusion gary!take care and stay safe!

Gary wrote:
April 29, 2012

The most the reloading manuals can get out of a 6-inch .357 Magnum barrel with 158-grain bullets is around 1250 fps. If you are getting 1400 fps or better, you either have a really long barrel, a Contender, or a bad chronograph.

attention to detail wrote:
April 28, 2012

those 125 grain 357 mag rounds must have been anemic loads to only clock 1270fps,i have 158 grain factory mag loads that clock 1400 or better!

Mack Missiletoe wrote:
April 25, 2012

A modern bottleneck auto cartridge? No thanks! It's not even a true .357! It's a .355--it's a 9mm +++p lol I hope it loses out and bad too--with that name! No way it will be more popular than 9mm or .40 with that bottleneck design. Why? Reloading. To call it a .357 is a sin & a marketing gimmick. Should have called it 9mm Super or 9mm Magnum. NOT .357. NO. Just NO.

Gary wrote:
April 24, 2012

If you are looking for .357 Magnum performance in a pistol, then the .357 SIG is for you. But you must remember that this miracle is accomplished by raising the pressure of the .357 SIG all the way up to 40,000 psi! That's 5,000 psi more than the .357 Magnum and 4,000 psi more than the .44 Magnum. I wonder if the manufacturers use fully-supported chambers or trust the brass case to hold. To withstand the high velocities produced, bullets must be on the "strong" side so expect expansion to be limited and penetration to be enhanced, if that is of importance to you.