38sp - 357 case capacity question

[kidneyboy]

I've been making a 38sp load from the Bayou160gr RN for years now and going to give it a try in 357.
The 38sp OAL is 1.560 and the 357 round will most likely be 1.590. The bullet itself measures .704.
My Lee second edition shows a useful case capacity of 1.30cc for 38sp and 1.36cc for 357
With this bullet set at these OAL's am I gaining any useful capacity going from 38sp to 357. My math (which is suspect) says I have .040" more space inside the 357 case when loaded to the aforementioned dimensions. Is this correct?

The pic below is a dummy round of each cartridge.

 

[AJC1]

You gain double the pressure limit which changes everything. Some people frown loading hot 38s because natural selection on the range is frowned on.

 

[kidneyboy]

You gain double the pressure limit which changes everything. Some people frown loading hot 38s because natural selection on the range is frowned on.

So, is my math correct?
I don't load hot anything anymore At best the 357 round will be a mid range load.
I don't have any load data for 160gr cast, coated round nose and I'm pretty sure I can use the same load data as for 158gr bullets. However, I have time to play around with the math and ask questions before I get started.

 

[.38 Special]

The internet strikes again.

The 160 is interchangeable with the 158. Assuming a gun in decent shape, any .357 data published by a mainstream source for a 158 lead bullet will be safe, and obviously will offer much higher velocity than can be obtained from a .38.

I have been involved in this game for many decades and until now have had utterly no idea how many cubic centimeters are displaced by any cartridge - and I will be attempting to forget what I have learned from the opening post as soon as possible.

 

[NMexJim]

You gain double the pressure limit which changes everything. Some people frown loading hot 38s because natural selection on the range is frowned on.

I like that - “natural selection on the range is frowned on”! Kinda like “Darwin never sleeps”.

 

[243winxb]

The 38sp OAL is 1.560 and the 357 round will most likely be 1.590.

This is .030" not .040" Or is my math wrong?

I gaining any useful capacity going from 38sp to 357.

The larger 357 case will use more powder to match the 38 case velocity. The only difference, being the brass length.

Looking at the photo, the same bullet, the 357 oal looks short. The 38 oal looks to long?

Go to tne Nosler website and compare 38/357 158 gr with SR4756. Gives a good idea of case fill & how many grains of water each holds. The water is to the base of the bullet, if i remember correctly?

The simple answer , use the correct loading data for each cartridge.

 

[FROGO207]

The usual bullet insertion depth/OAL is determined with the crimp groove when using a purpose built bullet in 38 SPL or 357. These days with limited supplies we tend to make due with what we can get. You need to use the data for the next heavier bullet and it's minimum OAL as a starting point to work up a safe load.

 

[kidneyboy]

This is .030" not .040" Or is my math wrong?

That is the difference in OAL between the two, yes. I'm looking for the difference in actual case capacity between them.

The 38sp cartridge is loaded kinda long but with 3.7gr of W231 its a very accurate plinking/target cartridge for my Henry and now the Marlin. When I started looking at loading that bullet in 357 at 1.590 it appeared that the case capacity for the 357 cartridge was about the same as the 38sp loaded with the same bullet at the slightly longer OAL.

 

[kidneyboy]

This is a math question about reloading, not a reloading question.
While I appreciate some of the advice above, I have plenty of load data (and experience) to work up a suitable load with the Bayou 160gr bullet in a 357 case.

 

[lordpaxman]

I agree with @243winxb , your math is wrong. Given the same bullet OAL, you gained .030” in the .357 case.

I’m not quite sure what the question is though, If you load the .357 .030” longer and the same powder/charge as the .38, you’ve got an anemic .357 load. If that’s what you want. Good luck.

 

[Walkalong]

This is a math question about reloading, not a reloading question.

Then I wrongly assumed the question was, assuming my math is correct, how much difference does that added space make.

 

[Rule3]

This is a math question about reloading, not a reloading question.
While I appreciate some of the advice above, I have plenty of load data (and experience) to work up a suitable load with the Bayou 160gr bullet in a 357 case.

They said "there would be no quiz"

 

[kidneyboy]

Then I wrongly assumed the question was, assuming my math is correct, how much difference does that added space make.

You are correct. I can figure out how much difference the added space makes if I know what the added space is.

I re-worded my original question several times before posting to try and make that clear.
Oh well......

 

[kidneyboy]

They said "there would be no quiz"

View attachment 1000962

You win!

 

[garandsrus]

I understand that this isn’t a reloading question thread, but you seem to have a whole lotta crimp on those rounds! It also looks like the bullet diameter is still increasing where you seated it. Why not seat the bullet longer in the 357 case?

 

[kidneyboy]

I understand that this isn’t a reloading question thread, but you seem to have a whole lotta crimp on those rounds! It also looks like the bullet diameter is still increasing where you seated it. Why not seat the bullet longer in the 357 case?

I keep a dummy round for each cartridge I reload. They get used to check my press setups when changing from one cartridge to the next. I have found that crimping them tight keeps them at their intended OAL from one setup to the next. It works for me.
The 357 cartridge in the pic is set at the SAAMI spec of 1.590.

 

[243winxb]

My crimp groove sets the OAL for me in 38 or 357. Never thought about capacity till now. I dont think i ever checked OAL on them. Just picked a listed powder for the cartridge.

 

[Rule3]

You win!

Without getting really into this.

If you take your known values of case capacity ( a 38 and a 357 case) which is in cc
You would need to calculated how many cc the seated portion of the bullet takes or occupies. The COL (cartridge overall length) has noting to do with the internal volume of the case assuming you seat the bullet to the same depth (seating depth)

For a visual you can cut both cases down the side with a Dremel. Then gently seat the bullet and see how much space is there.

or, You can use distilled water, fill each case and determine the volume.

357 vs 38 special case
Case length 1.29 in (33 mm) 1.155 in (29.3mm)

You are not dealing with a whole lot. As a "rule" of thumb not fact. Reduction of about 10% from 357 to 38 special, BUT pressure is no linear to big things can happen with just a tiny increase in powder (depends on the burn rate) seating depth etc etc etc,

 

[EricBu]

I'm not sure what powder you'd use that would require using all the case capacity of a 160gr cast .357 load. I mean, the only reason the .357 case is longer is to prevent it from being mistakenly loaded in a 38spc chamber.

 

[Jim Watson]

You are correct. I can figure out how much difference the added space makes if I know what the added space is.

Case capacity in the mathematical estimating programs is in grains of water to the base of the seated bullet.

One gunzine writer used gunpowder, I think H335, but any fine grained powder would work. As a measure of volume, NOT a shooting load.

I'm not sure what powder you'd use that would require using all the case capacity of a 160gr cast .357 load. I mean, the only reason the .357 case is longer is to prevent it from being mistakenly loaded in a 38spc chamber.

I am. IMR 4227 is shown by Lyman to be compressed in maximum loads for several bullets. Also 2400 and N110 in some instances.

 

[mcb]

Measure your case capacity yourself. It can vary from manufacture to manufacture. Take a fired case and put it on your scale and tare your scale. Then use a dropper to add water until it is level with the mouth of the case. This weight is the case capacity of your case in grains of H2O. Convert the grains to grams (0.0647989gr/g)and you have the capacity in cm^3 since the density of water is 1 g/cm^3.

 

[Blue68f100]

If you want to know the volume under the bullet. Leave the primer out and seat the bullet to the desired OAL you want. Then use something to hold the round nose down, weight or tare then and add water through the primer hole till full. This is the volume weight under the bullet.

 

[Elktrackstw]

My crimp groove sets the OAL for me in 38 or 357. Never thought about capacity till now. I dont think i ever checked OAL on them. Just picked a listed powder for the cartridge.
View attachment 1000966

I never check into figures that are irrelevant 38 cases are much thinner & designed for up to 20k psi 357 mag cases are much heavier & designed to withstand 37500 psi so loading weak low power loads in 357 cases makes it harder to seal off the case & get good seal in chamber...in other words
LOAD 357 loads in 357 mag brass ....load plinking loads in 38 brass
No reason to complicate it more than that.
I simply seat cast Bullets in crimp grove as well & shoot them at the length they are

 

[Walkalong]

X-Treme 158 Gr plated bullet over WST or Competition.
Gets plenty of pressure to keep cases nice and clean.
Very accurate, leaves guns as clean as any other good load.


But yes, a low pressure load in .357 Mag cases can indeed
be very dirty, especially with the wrong powder, and case
wall thickness is going to be part of the equation.

 

[murf]

volume of a cylinder is pi r squared h, so 3.14159 x (.357/2)^2 x .03 is .003 cubic inches which is .05 cubic centimeters. this is meaningless unless you know the total volume. so cut a case at the base of the seated bullet, fill with water, pour water into a graduated cylinder and read off the volume on the side of the cylinder. now you have an idea of how much a .05 cc increase in case capacity affects added case capacity. nothing will tell you how much that increased volume affects pressure and performance until you shoot the thing.

luck,

murf