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kirbinster 05-17-2013 02:02 PM

.357 magnum VS .38 spl question
I recently purchased a S&W686+ 4" stainless and love my new revolver. The first day I tried it I used some .38 special and said to myself wow this thing feels like shooting a .22 - almost no recoil just a slight push. The next time out I tried some .357 magnum and wow, the thing kicked and I really felt it in my hand. So, my question is how can there be so much difference in these two rounds that are the same diameter and only differ in length by roughly 1/10th of an inch. Both sets of rounds were from the same manufacture and were both 158 grains - so how do they stuff so much more power into that 1/10th of an inch? I looked up the energy difference and the .38spl is rated at 285 while the .357 mag is shown as close to double that at 548.

95sniper 05-17-2013 02:05 PM

Different powder charges, ect. I'm not an expert on this though.

kirbinster 05-17-2013 02:10 PM


Originally Posted by 95sniper (Post 1249560)
Different powder charges, ect. I'm not an expert on this though.

Can someone elaborate on this? I am a newbie and just assumed gun powder was gun powder -- I guess not.

nitestalker 05-17-2013 02:18 PM

Not recommended but a .38 Special can be loaded to near .357 Magnum pressure levels. The .357 Mag. was produced in longer cases to keep it from being fired in .38 Special revolvers.
You may also look at the ballistics of .38 Special Plus P ammo.:)

TekGreg 05-17-2013 02:20 PM

Fast burning vs. slow burning powder, magnum primers, form of powder (pellet, disc, etc.) all have a effect. SAAMI (Sporting Arms and Ammunition Manufacturers' Institute) sets the power levels that manufacturers must stay under for safe usage. .38 spl is a very old caliber, and even some older revolvers that were originally chambered for .38 spl must now use .38 short because pressure levels have continually risen over the years. .357 mag is a relatively recent chambering (compared to .38 spl) so the pressures are allowed to be much higher because manufacturers of .357mag handguns took these pressures into account. This is why a handgun chambered for ONLY .38 spl is usually much lighter in weight than a .38/.357 handgun such as yours - it doesn't need as much metal to handle only the lighter round.

So, basically, the .38 is loaded to a much lower standard, where the .357 has a lot of powder pushing the exact same bullet. The length of the case is only a safety feature to keep people from chambering a .357 mag in a gun only intended for .38 spl - it has no bearing on how much powder is actually used.

JW357 05-17-2013 02:24 PM


Originally Posted by kirbinster

Can someone elaborate on this? I am a newbie and just assumed gun powder was gun powder -- I guess not.

I'm no expert but at the very least 357s use "magnum" primers which I assume have more umph to them. I'm sure the powder is also different.

There are all sorts of powder. Some burn cleaner or dirtier, some faster or slower. I don't yet reload for 357 so I can't tell the best to use for the hotter loads. But as an example, with even just half a grain extra in powder, you will feel the recoil more substantially. I imagine you could get a fair amount of powder in that extra tenth of an inch or so.

Overkill0084 05-17-2013 02:26 PM

The standard .38 Special has a Max pressure of 17,000 psi. The .38 Special +P is rated at a max pressure of 20,000 psi.
The .357 Magnum has a max pressure of 35,000 psi.
The extra 1/10th of an inch has two functions:
1. It prevents loading a .357 cartridge into a .38 special camber.
2. It increases powder capacity, allowing for stouter charges.

Gun powders are products engineered to exacting tolerances for specific applications. Do some research into reloading and you can learn all the ins & outs of various powders. There are hundreds of powders available to the consumer, and probably as many again, that are not.
Even if you have no immediate plans to start reloading, learning about the variables and processes involved will give a better understanding of why things are the way they are.

John_Deer 05-17-2013 02:35 PM

Most 357mag loads are pretty hefty. If you look at a reloading manual 9.* grains is a starting load. The max load being well over 10 gr of powder. PPU factory ammo has 10.2 grains of powder under a 158 gr bullet.

nitestalker 05-17-2013 02:47 PM

The .357 Magnum grew out of "Hot" .38 Special loads. The S&W 38-44 large frame revolvers allowed .38 Special loads in the 30,000 PSI range in the 1920s. In 1937 S&W legitimized the hot .38s with the heavy frame Mdl. 27 in an elongated .38 Special case.
The popular load of the day was 16 grs. of 2400 powder under a 158 grs. bullet. There were no magnum primers in the day. Small rifle primers were used to contain the sever back pressures.;)

robocop10mm 05-17-2013 03:00 PM

Twice the pressure, twice the energy, twice the recoil. Kind of like the difference between a car with a 200 HP engine and the same one with a 400 HP engine. Night and day.

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