Gap in the data? .38 special - .357 question


November 2, 2009, 11:20 PM
I was reading the loads for 38 special and 357 mag with the same bullets (158 LSWC for Bullseye) I have read/heard that you can use 38 special loads in 357 brass no problem.

Does this mean that you can load 158 LSWC in .357 brass from 3.0 gr all the way up to the top of the .357 loadings? It's funny, since most data stops for the 38+p loads, but then the .357 load for the same bullet starts up a bit higher. So there is a gap in the loadings? These would be shot out of a 4" barrel, so I don't want to make any squibs.

I thought it would be fun to make up a range of loads in 357 cases, same bullet, all the way from light target 38 specials to low to mid range 357, to try to find a load which is the most fun, accurate, etc. More so than a 38 special wadcutter load, that is.

Does this make sense?

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November 2, 2009, 11:39 PM
Yes. Bullseye, Unique, and Herco are good choices for this exercise (there are other good ones too, of course.) Bullseye is unusually well behaved for a fast powder. The other 2 are medium powders.

Steve C
November 2, 2009, 11:41 PM
No reason why you can't or shouldn't do this. You may get slightly less velocicty using .357 mag cases with the .38 data than you would if loaded in a .38 spl case as the .357 mag a a slightly larger case capacity but it certainly will not be much. You would be unlikely to stick a bullet in the barrel of a handgun if using typical .38 spl start loads, just don't drop below the start level.

The "gap" you see in load data is just the difference between pressure levels of the 2 cartridges. The loading manuals assume that if you are loading the magnum cartridge you want magnum performance at its pressure capabilities so they see no need to continue a slow progression from .38 spl +P to mag loads.

November 3, 2009, 02:35 AM

There really isn't a gap, since we're talking about two different calibers, .38 Special and .357 Magnum. The data compiled in the manuals was never intended to bridge from one caliber to the next.

That's not to say that you can't do what you're attempting, it's just that the methodology is flawed. The .38 Special is loaded to a maximum of approximately 16,500 CUP, while the +P loading in this caliber is approximately 19,000 CUP +/- (I'm going from memory here).

The .357 Magnum maximum pressure is approximately 45,000 CUP, with most maximum loadings listed in the area of 40,000 to 41,000 CUP. The two cases are also constructed differently, with the wall and web of the .357 Magnum case being much thicker and stronger.

Sure, you can load most loads from .38 Special data into a .357 Magnum case. There is more volume in the .357 Magnum case, so velocities will in most cases be lower for the same data vs. the .38 Special case. There is a caution concerning minimum loads from .38 Special data loaded into the larger case. You don't want to stick a bullet in the bore, and the recommendation is to keep velocities of jacketed bullets over about 750 fps so the jacket doesn't stick part way down the barrel. With lead bullets, you can go a little lower, but not a whole lot.

Your project is "doable", but you just have to look at it from the proper angle and approach it as two different calibers. Map your velocities and you'll be able to correlate them into the loads you want.

Hope this helps.


Bailey Boat
November 3, 2009, 09:01 AM
Shrink, I'm currently in the process of doing what you're thinking of. At the present I'm calling it the "38 Magnum".........

Here's what I'm after. I have my survival rifles picked out, tricked out and ready to go and now I'm down to sidearms. My best and most logical choices (given the size of myself and the wife) are a K frame M 19, 4" for me and a J frame M 60, 3" for her, obviously both chambered for .357. Any .357 in the J frame is a handful but doable for the K frame. I don't want 2 different loads to keep track of so I'm developing something that is above 38+P but below a full 357.

Here's what I have so far, a 125 JHP, 357 cases (to keep them out of any 38 special) and a targeted velocity of 1100-1150 fps to insure expansion at close ranges but keep recoil manageable in the J frame. The choosen load MUST be accurate in BOTH guns and by accurate I mean 2" or less at 25 yards.

I'm through the first round of testing and I have several loads that gave me the accuracy but fell just short on velocity. I need to bump them by about 100 to 200 fps and see if the accuracy and recoil hold at their present levels. I have round two test loads ready for the range and will post those results as soon as I have them.........

November 3, 2009, 09:15 AM
Sounds cool. I'd be interested in your load data if you feel comfortable sharing it.

I plan on making up two loads, one a 125 JHP similar to what you are describing, for a J frame "bigger than a 38+P" load, and then also a 158 gr LSWC load for plinking and target practice.

Looking at the Lyman 49th edition manual, would bullet 358311 best approximate a 158 gr LSWC (I have the ones)? They say that bullet "duplicates the factory lead round nose 158 grain bullet very closely" So, according to the data for 38 special and 357 mag, Bullseye charges from 3.2 gr to 3.6 are 38 special, 4.1 being a +P max (this data in 38 Special cases), and then .357 magnum data from 4.9 gr to 6.9 max. The listed top velocity was about 1110 fps.

This sounds like a fun project.

November 4, 2009, 04:38 AM
Does this mean that you can load 158 LSWC in .357 brass from 3.0 gr all the way up to the top of the .357 loadings? It's funny, since most data stops for the 38+p loads, but then the .357 load for the same bullet starts up a bit higher. So there is a gap in the loadings? These would be shot out of a 4" barrel, so I don't want to make any squibs.
If a 3.0gr charge is safe in a .38 Special and the .357 Magnum data starts considerable higher there's no reason anything in between wouldn't be safe too. Squib loads are caused by too light a charge so anything above the minimum should be fine.

Bailey Boat
November 4, 2009, 07:06 AM
That's the same thing I noticed, the gap between the 2. What really surprised me was the published data on +P. It seems that the only thing that goes up is pressure. I even looked at the Speer site and the "famous" short barrel load doesn't break 900 fps.
I'm going to take some time today or tomorrow and section a +P case and a regular 38 and see what they look and measure like....

PS: the second test loadings will be going to the range tomorrow and I wouldn't mind sharing the data via PM only.....

November 4, 2009, 09:29 AM
When it comes to loading light for .357, but over max for .38 Spl loads in .357 brass you are kind of on your own.

I have done a fair amount of it. There is very little to no .357 data with fast powders. There is the .38 Spl data that can be safely used in .357 brass, but then we have to make up for the little bit of extra case capacity, and then we are really on our own. Using fast powders we can bridge that gap between what a .38 Spl load will be pressure wise and the max for .357 pretty quickly. Problem is we don't have pressure equipment to tell us where we are.

For more velocity than standard .38 Spl in .357 brass it is best to go to powders that give the best velocities in +P loads instead of the very fast powders. Still fast by .357 standards, but not the really fast powders. Then for Midrange loads good old .357 data with stuff like Unique works just great.

November 4, 2009, 10:11 AM
I load 5.0-5.2gr of Bullseye with 158 LSWC and WSP in .357 mag. for a 2.75" Ruger Sec. Six, shoots great.

November 4, 2009, 11:59 AM
The Speer manual mentions why specificly. The light loads in .357 brass is for shooting with their SWAGED lead bullets. They are made with soft lead so they can be made by swaging in their automatic machinery. Since they're made with soft lead, they can't be fired with as high a velocity as hard cast lead. Read Speer's statement on page 364 in manual #10

"The top lead bullet loads listed give the highest velocity obtainable with target accuracy and freedom from leading".

Their soft swaged bullets can't be pushed as fast as cast ones because they have to be made from soft lead. They stop when barrel leading becomes detrimental to accuracy.

I believe though that Speer's latest manual, #14, now lists loads for RCBS cast bullets. That's your best bet for the latest information.

For loading with your own hard cast bullets, you can start with the lowest starting velocities and work your way all the way up to magnum loadings. What you will find is that you can push HARD cast almost as fast as jacketed bullets, and I routinely shoot a cast SWC at about 1800fps in my .357 rifle with only minor leading that cleans out with a cotton patch. This is with homemade Lyman #2 alloy made from 19lbs of wheelweight lead with one pound of lead-free tin plumbing solder added. Makes fanstatic alloy for magnum bullets. Give it a try.

November 4, 2009, 05:47 PM
In the Lyman manual bullet 358477 is the closest to commercial cast 158 SWC. The same manual has some good suggested low - full on suggestions for .357's using jacketed bullets. No so many with regards to the heavier lead. I have used 5.5 - 6 grains of Unique with a 158 SWC with decent results. More of a .38 +P+ than a .357. I use a .357 loading of bulk Remington 125 grain JHP's and 7.5 grain of Unique in a Rossi Carbine, very mild and accurate, clean burn. What I would call a medium magnum. Hope this helps. Bill

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