Powder charge for .38 vs 9mm

OneHorseRanch

OneHorseRanch

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HI All!
I'm new at reloading. Reloaded a bunch of .380s and 9mm. All seemed to cycle through my firearms nicely. Now I'd like to reload my .38 Specials. I see in the reloading chart that the powder load minimum is 3, and max is 4grs. The 9mm I can load at max 5grs, both with W231 powder. Just curious why the .38 with a longer cartridge can take a lighter load? I'm sure this is a stupid question for most of you, but I'm hoping there is no such thing as a "stupid question".. so before I get started with these .38s I'd like to know the physics is why it's a lighter load than the 9mm. Thank you. A
 
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Welcome! What 'old tanker' said.
In the old days 38spcl were preferred for self defense, but with modern powders and bullets most like the 9mm. Higher pressures and increased velocity with bullets just about the same weights as 38's have to offer make for a nice hole.
I still like a slow 158gr piece of 38 lead. :)
 
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Also depends on bullet weight, which you don't mention as to what you are using or planning on using, and the bullet construction - swaged, cast or jacketed.
 
Keep in mind that bullets of different weights cause different pressure characteristics as well, with the same powder load. And every cartridge has different pressure limits.

Also the 38 Special is so long because it was originally designed for black powder. The 9mm was originally designed for smokeless, so it didn't need to be so big.
 
What I find more interesting is that there are a number of powder and bullet combos were the same charge would be appropriate in both 9mm and .38 Special. 9mm operates at approximately twice the pressure and yet the charge weights can be identical in certain circumstances.

The difference between the 2 cartridges being the case capacity. The same amount of powder is going to create the same amount of gas inside the case, but the pressure is spread out over a larger area and therefore the pounds per square inch are much less in .38 Special.
 
Cannot compare two totally different cartridges and two totally different platforms (guns). Each powder, powder charge for each different cartridge component combo has a huge number of variations. If just wanting theory, perhaps one could compare bullet weights and case capacities and gun types but I believe the number powders would make this a life long task (and for a much better mathematician than I am!) :rolleyes:
 
Ok, thanks! I did leave out a bit of info. W231 powder, lead semi wadcutter bullets 158 gr. I guess my question was: why so much less powder for the .38. I would have guessed that I would need more because of the extra cartridge length. I do have a RCBS loader with the Nosler book. What are your recommendations for grains for the .38? should I just go by the book or is there a magic number you folks wouldnt mind sharing.
 
Interesting tidbit...

OneHorseRanch said:
Ok, thanks! I did leave out a bit of info. W231 powder, lead semi wadcutter bullets 158 gr. I guess my question was: why so much less powder for the .38. I would have guessed that I would need more because of the extra cartridge length. I do have a RCBS loader with the Nosler book. What are your recommendations for grains for the .38? should I just go by the book or is there a magic number you folks wouldnt mind sharing.
Click to expand...

When smokeless came along and with better and stronger materials and designs some realized that the potential of the .38 case was much more than it was being used for. After blowing up a few .38 guns it was decided that the new cartridge, the .357 Magnum, was in a class by itself and is exactly the same case as the .38 except they make it about a hundredth of an inch or so longer so it can't be loaded into .38 Special guns. So they utilized that big empty space in the .38 Special.
 
Welcome to the loading wilderness. You've gotten good advice above. The 9 mm is designed for MUCH higher pressure in it's smaller case capacity. I use a lot of Win-231/HP-38 (same thing) and also some in 9mm, but I don't have my records with me and wouldn't quote my own loads anyway. Yes, follow the reloading manuals precisely for powder weight and bullet weight/type. It is ALWAYS advised to start your load work up from the bottom of the range of published data and move higher only as you note characteristics of the charge. Also note that every individual gun will have different results depending on chamber, barrel size, etc. That's why you have to do the testing yourself with your gun. The bullet manufacturers as well as the powder manufacturers have dependable data. It is a good idea to have several manuals and cross check between them. That opens up another can of worms as they may sometimes have different starting and maximum loads. When you see that, come back with more questions. Have fun and good shooting!
 
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OneHorseRanch said:
should I just go by the book or is there a magic number you folks wouldnt mind sharing.
Click to expand...

This is the single most important piece of reloading advice you will ever get:

Always go by the book.


(Years from now, when you're a highly accomplished hand loader working with some cutting edge wildcat cartridge, there won't be a book. Most of us never get there.)

Meanwhile, Happy Shooting.
 
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Also .38 is in the revolver platform where spent gasses can escape. Not so in the .380 and 9mm where the gasses are captured to operate the slide.

And go by the book, starting at the low end and working your way up. There's no way around this - no one can truly offer a short cut!

Sent from my Pixel 4 using Tapatalk
 
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rwsmith said:
When smokeless came along and with better and stronger materials and designs some realized that the potential of the .38 case was much more than it was being used for. After blowing up a few .38 guns it was decided that the new cartridge, the .357 Magnum, was in a class by itself and is exactly the same case as the .38 except they make it about a hundredth of an inch or so longer so it can't be loaded into .38 Special guns. So they utilized that big empty space in the .38 Special.
Click to expand...
Just a minor correction: The 357 is fourteen hundredths of an inch longer than the 38 - not just one hundredth of an inch longer (357=1.29" & 38=1.15").
 
OneHorseRanch said:
Ok, thanks! I did leave out a bit of info. W231 powder, lead semi wadcutter bullets 158 gr. I guess my question was: why so much less powder for the .38. I would have guessed that I would need more because of the extra cartridge length. I do have a RCBS loader with the Nosler book. What are your recommendations for grains for the .38? should I just go by the book or is there a magic number you folks wouldnt mind sharing.
Click to expand...

The 38 case has 2x + the volume as 9mm. So with identical powder charges & bullets, pressures will be quite a bit less in 38sp.
 
One factor I didn't see mentioned above is that smokeless powders are progressive. The more they are confined they faster they try to turn into a gas. The exact same amount of powder behind a 158 grain bullet will produce more pressure than the same amount behind a 125 gr bullet.
6.1 gr of Unique will produce about 950fps with either bullets. With a 125 gr bullet it is a minimal load and with a 158 a maximum.
 
rwsmith said:
....357 Magnum...longer so it can't be loaded into .38 Special guns...
Click to expand...

The .38 S&W Special cartridge was a lengthened version of the .38 Government cartridge then in use. Developed for Smith's new Military & Police revolver early versions of the revolver included the ".38 US Service Cartridge" designation as S&W was disinclined to stamp .38 Long Colt on their product.

The .38 Long Colt, like other cartridges whose roots go back to percussion conversions, initially used heel based bullets. Most of those old Colts had cylinders that were bored straight through. Lacking the "step" in the chamber those Spanish American war era Army issue revolvers will chamber a .357 magnum.
 
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old tanker said:
The .38 S&W Special cartridge was a lengthened version of the .38 Government cartridge then in use. Developed for Smith's new Military & Police revolver early versions of the revolver included the ".38 US Service Cartridge" designation as S&W was disinclined to stamp .38 Long Colt on their product.

The .38 Long Colt, like other cartridges whose roots go back to percussion conversions, initially used heel based bullets. Most of those old Colts had cylinders that were bored straight through. Lacking the "step" in the chamber those Spanish American war era Army issue revolvers will chamber a .357 magnum.
Click to expand...
Yes, unfortunately they will.
Have to be careful with this one not to put the wrong ammo in it.
Though I have read that they will handle the pressures of 38 Special, that isn't something I want to test and I see no point in beating up such an old gun when I can easily create safe loads for it.
 

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Go by the book ... in reloading ALL the details matter.

There is no magic number .

After casting and reloading for over 50 years I can tell you it's best not to push over the Maximum loads in your reloading manual ...
unless you are very experienced and have the equipment to safely check what you are doing ... max loads are not to be ignored and must be worked up to slowly ..
Gary
 
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