.357M Dilemma for Experts.

[avcrew]

Using two primary powders for pistol loads. HP38 and Unique. I matched velocities for .38S, 9mm, .45ACP, .44M. In each case, the Unique loads were always .1 to .4 grains higher to match velocity of HP38.

Examples:

All loads chronographed with a minimum of 15 shots per load.

.38S 158g LRN / CCI 500 primers / all fired from S&W 686 4"
3.8 grains HP38 = 650FPS
3.9 grains Unique = 650 FPS

9mm 115 grain Berry's plated round nose / CCI 500 primers / all fired from Sig P226
4.6 grains HP38 = 1100FPS
5.0 grains Unique = 1100FPS

.44M 240 grain Missouri LFP bullet / CCI 300 primers / all fired from S&W 629 4"
7.0 grains HP38 = 900FPS
7.2 grains Unique = 900FPS

.45ACP 230 grain Berry's plated round nose / CCI 300 primers / all fired from Kimber FS 1911
5.3 grains HP38 = 825FPS
5.5 grains Unique = 825FPS


Now when I load for .357M, here are my results:

.357M 158 grain Berry's plated flat point / CCI 500 primers / all fired from S&W 686 4"
5.2 grains HP38 = 860FPS
5.4 grains HP38 = 902FPS
5.2 grains Unique = 890FPS
5.4 grains Unique = 917FPS

WTF?

Velocity for Unique is higher for the same weight of powders.

I would reason that to match the velocity of 5.2 grains of HP38 (860FPS), that I would need about 5.4 grains of Unique. This wasn't the case. At the same weight of 5.2 grains of Unique, the velocity was already 30FPS higher.

Any explanation?

[sghart]

[Pardini]

What's the dilemma?

[Jta]

Case length and size = voodoo magic
Also using only two examples to form a conclusion is sort of like saying “I rolled a dice two times, both times were even numbers so the next roll must also be an even number”.

[kcstott]

Using two primary powders for pistol loads. HP38 and Unique. I matched velocities for 9mm, .45ACP, .44M. In each case, the Unique loads were always .2 to .4 grains higher to match velocity of HP38.

Examples:

9mm 115 grain Berry's plated bullet
4.6 grains HP38 = 1100FPS
5.0 grains Unique = 1100FPS

.44M 240 grain Missouri LFP bullet
7.0 grains HP38 = 900FPS
7.2 grains Unique = 900FPS

Now when I load for .357M, here are my results:

.357M 158 grain Berry's plated flat point
5.2 grains HP38 = 860FPS
5.4 grains HP38 = 902FPS
5.2 grains Unique = 890FPS
5.4 grains Unique = 917FPS

WTF?

Velocity for Unique is higher for the same weight of powders.

I would reason that to match the velocity of 5.2 grains of HP38 (860FPS), that I would need about 5.4 grains of Unique. This wasn't the case. At the same weight of 5.2 grains of Unique, the velocity was already 30FPS higher.

Any explanation?

As others have said this is not how this works.

what you need to look at is load manual data and compare that way and you'll see the same results.

You didn't account for barrel length, different primers, different bullets.

you can not take data for two powders from one caliber and apply the result to another caliber. if you could you'd only need data for two rounds, rifle and pistol. and we know it don't work that way.

[avcrew]

As others have said this is not how this works.

what you need to look at is load manual data and compare that way and you'll see the same results.

You didn't account for barrel length, different primers, different bullets.

you can not take data for two powders from one caliber and apply the result to another caliber. if you could you'd only need data for two rounds, rifle and pistol. and we know it don't work that way.

Added another example. Added more data. All primers the same. All bullets fired from same respective gun. Not making any conclusions, just an explanation.

[sunnysmarine]

just a few things that come to mind, case volume and wall rigidity, bullet type, insufficient primer strength, pistol barrel versus revolver barrel, bullet jump causing pressure spikes or loss of pressure. you are comparing apples to oranges, try the 38 Spec. and 357Mag start with starting loads for both and work up in 0.2 grain increments maybe be at some point the powders will respond completely opposite are the 38 Spec and 357 mag datum from the same firearm that would remove another variable

[kcstott]

just a few things that come to mind, case volume and wall rigidity, bullet type, insufficient primer strength, pistol barrel versus revolver barrel, bullet jump causing pressure spikes or loss of pressure. you are comparing apples to oranges, try the 38 Spec. and 357Mag start with starting loads for both and work up in 0.2 grain increments maybe be at some point the powders will respond completely opposite are the 38 Spec and 357 mag datum from the same firearm that would remove another variable

Agreed and....

wait till he starts reloading rifle ammo and finds when you hit a pressure node velocity will not change till you get a good .5 grain more on the case. you keep adding powder and nothing happens?? yeah well that's a pressure node.

[TexasJackKin]

I like SGHart's response, That's not how it works. No issue, you just got results different than what you expected. I get that, I'm curious as to why, but some times just have to accept the results. That's why we have loading manuals, you can wonder about what's going on, without ever firing a shot.

In your case, case volume and burn rates, come into play, and at some point you just have to accept...That's just the way it is....

On a side note, I get more constant velocity using CCI 550 (Magnum) primers with light loads of HP 38, in .38Spl.

[DueceMcGurk]

Good work. Thanks for sharing. I get load/velocity/accuracy anomalies using the same gun, and reload components. :-) There are many gremlins in reloading. Sometimes trying to make it a science can be frustrating. But I still do it.

[J-cat]

When you combust powder you create energy. That energy then accelerates the bullet. Efficiency of combustion determines how much energy is produced. Factors affecting efficiency of combustion include pressure and the shape of the pressure vessel. You are going to see different results in long skinny vessels vs short fat vessels. Maybe that explains your anomaly.

[avcrew]

Alright. Starting to make some sense.

The .357 case is a long case suited to hold as much as 20 grains of powder.

My .357 loads are quite mild, using only 5.0 to 6.0 grains of powder, leaving lots of case volume left over.

HP38 is more dense. Unique is more fluffy and takes up more case volume per same weight as HP38.

At my tested loads, case volume and pressure are coming into play.

.357M 158 grain Berry's plated flat point / CCI 500 primers / all fired from S&W 686 4"
5.2 grains HP38 = 860FPS
5.4 grains HP38 = 902FPS
5.2 grains Unique = 890FPS
5.4 grains Unique = 917FPS

At 5.2 grains of each powder, Unique is 30FPS faster than HP38.
At 5.4 grains of each powder, Unique is now only 15FPS faster than HP38.

So, it stands to reason, if I were to continue loading up, taking up case volume and increasing pressure, HP38 may perform as expected vs Unique, which is .1 to .4 grains less powder to achieve the same velocity.

Only one way to find out for sure. More testing.

[avcrew]

Just wanted to post an observation.

As leftover case volume diminishes, the amount of Unique required to equal HP38 velocity, goes up.

My .38S load (most leftover volume) required .1 grains more of Unique to = HP38.
My .45ACP load required .2 grains more of Unique to = HP38.
My 9mm load (least leftover volume) required .4 grains more of Unique to = HP38.

[Fishslayer]

Different powders react to different conditions... well.. differently. Burn rate is only one quality of a powder.

sghart nailed it.

[avcrew]

New expanded results. Loaded up 15 rounds each.

.357M 158 grain Berry's plated flat point / CCI 500 primers / all fired from S&W 686 4"

5.2 grains HP38 = 876 FPS
5.4 grains HP38 = 909 FPS
5.6 grains HP38 = 931 FPS
5.8 grains HP38 = 975 FPS
6.0 grains HP38 = 984 FPS

5.2 grains Unique = 908 FPS
5.4 grains Unique = 917 FPS
5.6 grains Unique = 927 FPS
5.8 grains Unique = 946 FPS
6.0 grains Unique = 969 FPS

From the results:

At 5.2-5.4 grains of the the same weights of powder, Unique has a higher average velocity than HP38.

At 5.6 grains of the same weights of powder, HP38 and Unique have almost the same average velocity. 931 FPS for HP38 and 927 FPS for Unique.

At 5.8-6.0 grains of the same weights of powder, HP38 now has a higher average velocity than Unique.

5.8 grains of HP38 almost = 6.0 grains of Unique. 975 FPS to 969 FPS.

My conclusion, that Unique loads can be expected to be .1 to .4 grains higher to match velocity of HP38 for most pistol cases. Case volume and burn rates may change that.

I accept the theory that case volume and pressure played a part in skewing my expected results. Thanks to those who pointed in that direction.

In this case, .357M, I theorize that as case volume is diminished, HP38 will produce a higher average velocity over Unique for the same weights of powder.