.38 sp loads in .357 brass with SPM primers - is it a wash?

[barnfrog]

I've read advice indicating that if you use .38 special loads in .357 magnum brass you should increase the starting load by about 10% to account for the added case capacity. I've also read that if you're using magnum primers in loads that call for standard primers you should drop the load by about 10% to account for the slight increase in pressure. So if I'm using .38 special loads that call for standard primers but loading them in .357 brass and using magnum primers would I just use the .38 special load data? Seems to make sense, but being relatively new to this game I thought it was worth asking in case there's something I'm missing. In all my googling I don't think I found any responses that dealt with both adjustments, just one or the other.

 

[rfwobbly]

Trick question !
I would use my chrono.

I would find the listed Velocity for the Max Load of the 357M with that bullet and powder, and not exceed that velocity. That's all that matters. What we focus on in reloading is Chamber Pressure. And the velocity is the easiest way to get a handle on the CP.

It's easy when you start mixing components to loose sight of that simple fact.

 

[AzShooter1]

I've used Magnum primers in my .38 loads with no problem for many years. I find I get about 50 FPS more muzzle velocity.

Using .38 loads in your .357 is also not a problem as long as you are not using minimum loads like 2.5 grains of Bullseye with a 148 grain wadcutter. I'd up the powder charge 10 to 15% to be safe.

A good bet for low velocity loads in .357 cases is to use Trail Boss powder. Very low recoil, no smoke and no unburned flakes of powder.

 

[barnfrog]

Understood, and good reminder, thank you @rfwobbly .

But that only helps me keep from going over the max pressure once I've started working up. Perhaps the question should be restated to ask what starting load to use and work up from, instead of what load data range to use.

 

[Walkalong]

I doubt it's a "wash", but I also doubt it could hurt. I don't have any .38 Spl loads with mag primers, so I would not use mag primers running one in .357 Mag brass. It also won't hurt running any near full or full power .38 Spl loads in Mag cases with no changes. Start there, and if you need to bump it a hair to get the same velocity and want to, do it.

 

[barnfrog]

Using .38 loads in your .357 is also not a problem as long as you are not using minimum loads like 2.5 grains of Bullseye with a 148 grain wadcutter. I'd up the powder charge 10 to 15% to be safe.

Actually, that's close to what I'm looking at doing. Based on three different data sources, I was thinking of around 3.0 grains of Bullseye, AA #2 or Red Dot under plated double ended wadcutters. Consensus seems to be data for cast WC can be used with plated.

 

[2ndtimer]

Actually, that's close to what I'm looking at doing. Based on three different data sources, I was thinking of around 3.0 grains of Bullseye, AA #2 or Red Dot under plated double ended wadcutters. Consensus seems to be data for cast WC can be used with plated.

If you are using .357 Magnum cases, small pistol magnum primers, and firing them in a .357 Magnum revolver, why wouldn’t you simply use published .357 Magnum load data? Seems like you are overthinking it.

 

[barnfrog]

If you are using .357 Magnum cases, small pistol magnum primers, and firing them in a .357 Magnum revolver, why wouldn’t you simply use published .357 Magnum load data? Seems like you are overthinking it.

Because most of the manuals I have include .38 Special data for these powders with wadcutters, but some of them don't have .357 Magnum data for the same combinations.

Also, I have a lot of SPM primers and very few SP primers. Maybe it's time to use those SRPs I have that won't get used for anything since I don't load any cartridges that use SRPs.

 

[2ndtimer]

 

[243winxb]

Much to my supprise

Hodgdon has 12 powders listed using WSPM & Hornady 148 gr LHBWC in 357 magnum.

Use starting loads, work up.

 

[tightgroup tiger]

If you want to load 38 spl loads in .357M brass and only have SPMP then use them. It certainly won't hurt anything since you have to shoot them out of a .357M revolver anyways.
Can you do it? Sure. Will it hurt anything? No. If it's all you can get then use them.
38 spl loads = 17500psi. .357 mag revolvers can handle 35k+ psi. Not going to hurt the revolver if a little more pressure from magnum primers happens.
You don't need to reduce your 38spl load at all when using magnum primers.

 

[GeoDudeFlorida]

In my experience it’s not quite a “wash”, more like a step up the ladder. So if you’re in the start to middle .38Spl range, even with a magnum primer, you’re still on the low side for .357Mag but perfectly safe. Might even be a better load than the magnum starting load. Depends on your gun. The catch being, we’re just talking handguns here, not lever carbines or single shot rifles. Then my advice would be different because plated tends to be stickier than coated or wax lube.

 

[barnfrog]

View attachment 1123579 View attachment 1123579 View attachment 1123579

Yes, Speer is one of the manuals I have, but that data is for a hollow base wadcutter. Doesn't the hollow base have the same effect as increasing the case capacity, thus making the data not equivalent to data for a double ended wadcutter?

 

[barnfrog]

Much to my supprise

Hodgdon has 12 powders listed using WSPM & Hornady 148 gr LHBWC in 357 magnum.

Use starting loads, work up.

Again, hollow base bullet.

 

[rsrocket1]

A lot has to do with the powder. For a fast burning powder, it won't matter if you use a SP, SPM, SR or SRM. The powder will fully ignite very quickly and burn fully within the first few milliseconds and be completely consumed by the time the bullet exits the barrel. For a slow burning magnum powder, it would make a difference. The "magnum" primers will burn hotter and longer and ignite more of the powder sooner. Magnum primers are meant for cases full of powder and usually slow burning ball powder.

Since you're loading 38 Special loads, you are probably using a medium to fast powder. I use SP, SPM, SR and SRM's interchangeably with my 9/38/357/45ACP loads and have seen virtually no measured MV's from my chronograph data. This is with powders as fast as Clays/Titewad/Competition and as slow as BE-86 and Power Pistol.

 

[cfullgraf]

Any max pressure 38 Special load will be safe in 357 Mag revolver even if loaded in a 357 Mag. case. It may be a bit slower.

Any minimum 38 Special load in a 357 Mag case may not be fast enough to prevent the bullet from sticking in the barrel. Not a good thing. If you are working near the minimums, make sure the bullet exited the barrel before firing the next shot. You do not to shoot a bullet into a barrel with a bullet stuck in it. When you are sure every bullet is exiting the barrel, then you can do some rapid firing.

Most reloading manuals, the maximum 38 Special loads are usually lower than the minimum 357 Mag loads. Since it is safe to shoot 38 Special ammunition in a 357 Mag revolver, down loading a minimum 357 Mag load a bit will be safe.

On caveat to this, not all powders work well at reduced loads. Winchester 296 and Hodgdon H110, they are the same powder these days, do not play well at charges more than about 3% or so below maximum. The pressure gets erratic at downloaded powder charges.

I do not need to shoot full power 357 Mag loads much any more. I keep some full power loads on hand just in case.

My usual 357 Magnum ammunition is a 158 grain SWC loaded to about 1000 fps from a 4” revolver. A bit hotter than 38 Special ammunition but no where near 357 Mag top velocities.

I’ve fired a boat load of target 38 Special ammunition from my S&W Model 19 (357 Mag) revolver without issue. I’ve recently acquired a couple 38 Special Model 14 and Model 15 revolvers so I save my 38 Special cases for them.

Magnum primers used with 38 Special loads in a 357 Magnum revolvers is a non issue safety wise. 38’Special loads do not need magnum primers, magnum primers are scarce these days but are needed for difficult to ignite powders. But, economic and supply conditions may dictate otherwise.

If you are looking to match a particular round or match a particular velocity, you need to get a chronograph.

Lots of good advice already posted.

I hope this helps.

 

[film495]

you can probably cross reference some examples with online resources. I bet what you are saying is mostly correct, but I'd want to see data to back it up. I don't think I would substitute what you are saying unless I found a published 357 load to match to what I was handloading. I've messed around with a few things and one thing I try to remember is you might use one primer or another, but - at the end of the day you should be able to find a published load from one of the big books, that really closely matches what you are loading, and if there isn't there is probably a good reason why.

 

[Otto]

Magnum primers will make a negligible difference.
I’d be more concerned with temperature inverse powders in the winter.

 

[2ndtimer]

Yes, Speer is one of the manuals I have, but that data is for a hollow base wadcutter. Doesn't the hollow base have the same effect as increasing the case capacity, thus making the data not equivalent to data for a double ended wadcutter?

The Speer No. 10 shows .38 Special load data for their solid bevel base wadcutter, as well as their hollow base wadcutter. Note the increased powder charges for the bevel base bullet compared to the hollow base. Point being you can safely load heavier charges in your .357 cases without pressure concerns. The greater concern would be loading too light and sticking a bullet in the barrel.

 

[barnfrog]

Good advice from everyone, as usual. Thanks for contributing to my safety.

Question pretty much answered mods, so you can lock this one up as far as I'm concerned.

 

[N555]

Yes, it's a wash. I found putting a start load or slightly less than a 357 start load of fast burning powder in a 38spl case cut standard deviation in half and knocked at least 20 to 30fps of the extreme spread.
I would hate to think what putting a 38spl load in a 357 case would do.
I think if you did that my extreme spread would become your standard deviation or worse.
I save 357 brass for the heaviest magnum loads using H110, AA9, 2400, ect.

 

[Palladan44]

With .38 Special loads, and fast burning pistol powder like Red Dot, Clay's, or W-231 the case - fill % is pretty darn low. Meaning a lot of air space in the case as it is.
A position sensitive powder will begin to act up as it is. Most of them work just fine, though. No problem.
In fact I don't know of any modern .38 SPL load that DOES NOT leave at lest 1/4" or more of airspace left in the case. Due to the case being low SAAMI pressure due to originating prior to modern smokeless powder. Same for 45 LC, 45-70, 44 SPL, etc. Etc...

In 357 brass, the pressure and velocity will be lower for the exact same load as a .38 SPL. Having to Add around 8%-10% more powder for the same result as a .38 SPL is fairly common. I'd stick with the .357 Mag lead data that's out there......there is a ton of it.

 

[CoalTrain49]

A lot has to do with the powder. For a fast burning powder, it won't matter if you use a SP, SPM, SR or SRM. The powder will fully ignite very quickly and burn fully within the first few milliseconds and be completely consumed by the time the bullet exits the barrel. For a slow burning magnum powder, it would make a difference. The "magnum" primers will burn hotter and longer and ignite more of the powder sooner. Magnum primers are meant for cases full of powder and usually slow burning ball powder.

Since you're loading 38 Special loads, you are probably using a medium to fast powder. I use SP, SPM, SR and SRM's interchangeably with my 9/38/357/45ACP loads and have seen virtually no measured MV's from my chronograph data. This is with powders as fast as Clays/Titewad/Competition and as slow as BE-86 and Power Pistol.

I was going to post something like this but that covers the situation very well. It's the powder that you should be concentrating on when using magnum primers. For instance, I load 357 using 2400 without mag primers. Not an issue because 2400 isn't a ball powder.

The OP never did state the powder he wanted to use, just the primer.

I load to 38 spl velocities using 357 cases and a fast powder. Primers aren't going to matter here.

 

[barnfrog]

I was going to post something like this but that covers the situation very well. It's the powder that you should be concentrating on when using magnum primers. For instance, I load 357 using 2400 without mag primers. Not an issue because 2400 isn't a ball powder.

The OP never did state the powder he wanted to use, just the primer.

I load to 38 spl velocities using 357 cases and a fast powder. Primers aren't going to matter here.

I did state the powders, but not in the first post. In post #6 I said I was looking at using Bullseye, AA#2 or Red Dot.

 

[Rule3]

Late to the party here, Mag primers is not gonna make much difference, A little may depend on the powder, some are harder to ignite but in 38 special you are not using them

Hodgdon in their data for anything that says magnum uses a mag primer even it the powder is say HP 38.