I was hopping to find why the different loads I have had shot over the Chronygraph, 38 super, 45, 9mm compared to 38, 357 loads as the shorter cases produce more consistent loads (as they are all within 25fps of each other), the loads for 38/357 have a greater spread, about a 60fps.
e.g.
38 super 125 grain conical projectile with 4.6grns of winchester 231:
1000fps
998.1fps
985.5
1010fps
990.9fps
357 125 conical projectile with 5.2grns of winchester 231
942fps
938fps
850fps
883fps
875fps
My question is how can I make the 38/357 loads be more consistent?

Because the loading density is higher.

Simply put, the charge fills a larger percentage of the case volume, resulting in the charge being held in closer proximity to the primer and more consistent ignition. It reduces position sensitivity.

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Gunsmithing since 1961

Smaller cases allow the powder to fill properly. If the case isn't full, the powder can slosh around in there and you will see a lot of inconsistent burns.



Here the top image is what you want. IF the case isn't full, then depending on how the cartridge has been handled either of the second two situations can occur and obviously, the power will burn differently.

Part of my powder selection and measure involves insuring that the case is full when the bullet is seated. Long rifle cases require the same thing.

Yes, I realize this is grossly exaggerated but it does illustrate the point.

So if I filled up the case, the 38 or 357 by using a slower burning powder I would get a more consistent load for the chrony? Any particular powder I should use, I do have Trailboss for the 45-70 pistol that I use, would that be good enough as the speed would only have to be around the 800 fps mark? Can you suggest any other powder I could use?

Unique fills just about everything.

60 fps difference in not that bad for a 38 spl. I get tighter chrono #'s using WST, but still use other powders like PB for my practice loads. PB at slower speeds really has a larger fps spread, but tightens up nice as the speeds go up.
The chrono does tell you a lot, but at 25 yards, it amazing how accurate these guns are, even when the chrono shows a wide spread.
50 yards might be a different story.

In long cases with light powder charges consistancy can often be
improved by using magnum primers. The effect on velocity will not be
significant. Some powders are more position sensitive than others but
in general, consistancy of chronograph readings is improved by
tilting the gun muzzle up before each shot to position the powder back
against the primer. This is not always possible of course when using
your gun in the field. Trying to fill the case when loading light loads
isn't really practical unless you want to use something like expensive
Trailboss for all loads. The best powder I have ever used for light
loads is the discontinued W452AA. No position sensitivity whatsoever.
It's replacement, WST is not so forgiving. Titegroup and Bullseye
are less position sensitive with light loads than most powders in my
experience. W231 is better at higher pressure levels.

Hard to say without knowing more about your process, especially your crimping, if any, of the .38/.357.

But, I suspect it has more to do with your particular guns than anything else. Hard to compare apples to oranges. Tough to compare .45acp shot form gun A. with .357 mag shot from gun B.

__________________
USAF, 69-92
Vietnam, 72-73

Rifle & handgun calibers benefit from short, fat powder columns. They burn more uniformly & create pressures more uniformly. This almost always helps shot to shot variations.

__________________
NRA Cert. Inst. IDPA CSO

On another forum it was agreed a firm crimp on 38/357 and 44spl/44mag loads helps get the powder burning more efficiently. I would think this might lead to more consistent FPS. If I had a chrono I'd try it!
After firing some of my 357mag loads I was finding unburned powder on the shooting bench, mostly with 2400. A firmer crimp and that went away.

While low SD numbers are good to have they don't always translate into more accurate ammo. Over the years I have tested some factory ammo that produced triple digit SD numbers that were surprisingly accurate. I'm not saying that's always the case but i would not throw away a load only because the SD numbers are higher than you think they should be. Test the accuracy first and if it's good, then the load is also good.

Welcome to the forum...

BTW, you will probably like HS-6 with that .357 Magnum load you mentioned.

__________________
Freedom is never free!!
SWCA #3437

Thanks for all your help as I do appreciate it. I do have some WW452AA I bought many many years ago and I would have thought it would be a little bit off by now, since I have used half of it, it has been in the cupboard all these years.
I do have a good crimp on the bullets not a heavy one, just enough to see and feel it.
When I talked about the different loads of the 45, 9mm 38/357 I meant comparing the shorter cases to longer cases as the shorter ones fill up more so and do have a more consistent fps from the chrony.
And as you have stated a slower burning powder would fill the case up nicely and depending on the amount would be ideal and an accurate load.
If you say that 60 fps is nothing to worry about as it all depends on the end result at the 25 metre (sorry 25 yard) range as accuracy is the important fact here then I will find a comfortable load that is accurate and has the fps I require.
I do have some 2400 powder and as stated before some WW452AA I will try some loads out with the chrony and find an accurate load.
As a matter of interest how long does powder last for if kept dry and in a cupboard away from the sun etc and little fingers. I have some powder that is 20 odd years old?
Thanks for all help.

Marke I have part of a can left of W452AA that I bought in the early
80s, making it 30 yrs old and it is fine, very consistant. I have read
that one advantage to ball powders in general is their almost
unlimited shelf life if stored properly. Pistol powders in general seem
to have a much longer shelf life than the extruded rifle powders. 20
years is nothing to worry about.

You can easily tell if the powder is good or bad. Take a look at it and if it looks like there is rust in it, it's bad. Smell the powder and if it smells like chemicals it's good, if it smells a little rotten it's bad. After you determine it's good of course the only real test is to load it up and shoot...

Considering W452AA has a burn rate similar to Green Dot it will be just fine for loading the 45 Auto and .38 Special. It will also work fairly well for the 9mm but for the .357 Magnum, it will not deliver real magnum performance. W452AA was also sold as Hodgdon Trap 100 and I think it's replacement in the Winchester catalog was WST.

__________________
Freedom is never free!!
SWCA #3437

A full case in the 38 or 357 for best accuracy is not a 100% thing..........
I have several light loads and several full to compressed loads that are both accurate and some that are just terrible !!

I have also had loads that had a high ES of 125 or MORE, that out shot loads that were under 40 ES.

A lot depends on the powders burn rate and design...... but I have noticed that you just have to see what powder and amounts work in your guns.
I never know what a load will do when I test them. Some turn out great and others just make you scratch your head and wonder what the heck, just happened?

VV TinStar has a low density and fills more of the case. I just got some, but have not had a chance to load any test loads. It is marketed for cowboy loads. So if you are looking for target velocity loads, it might work for you. It has been compared to Trail Boss.

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Reg. Magnum wants/Rossi wallet

Thanks ArchAngelCD I will check out the powder as you have said and if good I will use it on the 38 and probably use it on the 357 light loads of course. As a lot of you have stated it is best to find a load that is both accurate and comfortable to shoot which I will do, but I will still put them over the chrony and see what they are doing.
I have found a powder here in Australia, a company called ADI, I am trying out there AP100 which on a powder burn rate chart (used as a rough idea only) is equal to SR 4756, so I will try out some different loads and see what happens.
Thanks for all your help, it has been interesting to say the least.

To answer the original question.

Combustion Chamber Design.

This is a big deal for internal combustion engines.

A teeny 380 can propel a 95 grain almost as fast as a 38 special with similar pressure.

Back when it was Black powder, the bigger case was better.

David

Not sure about the hodgdon trap, but wst is a slightly "cleaned up" version of 452aa. I used to shoot a lot of 452aa, when they switched, I found load data almost identical.

__________________
NRA Cert. Inst. IDPA CSO

Trap 100 was the same powder as W452AA just as HP-38
and W231 are the same. W452AA was discontinued back
in the early 80s I think and it's replacement is WST. I have
some of both and their appearance is quite different but the
load data is almost identical. For light handgun loads I like
452 better because it is virtually non position sensitive and
more consistant than WST. I have even chronographed many
light cast bullet 38 spl loads where 452 showed reverse
position sensitivity, slightly higher velocity when the powder
was positioned forward against the bullet than when back
against the primer. I mentioned this to a Hodgdon rep on
the phone one day and he basically called me a liar. I told
him I had seen it happen many times and to try it himself.
He just got angry and told me he wasn't going to waste
his time on nonsense. Oh well, another "believe me, not
your lying eyes" kind of person I guess.