Unique hotter?

[willy]

Got a chrono a few months back and started checking my hand loads.
My loads were on average 100 fps faster than the manuals show with unique.
Checked with another chrono and the results were the same.
This is with 38spl,,44spl,44magnum ,45 colt and 45acp.
This is only with unique powder.
But my loads are close to published loads with 2400 and 231.
Anyone else notice higher velocities with unique?

[fc60]

Greetings,

Not Unique; but, I have an old lot of Red Dot and a current one. About 100FPS difference.

Both dispense 4.0 grains with the same powder bushing.

The old lot does parallel the load in my early Lyman and RCBS books.

Cheers,

Dave

PS The chronograph is your friend.

[nicholst55]

What is the vintage of your Unique? Some of us can recall when what is now called 'old Unique' was 'new Unique' at the time. The burn rate has changed slightly over the decades, which could explain your velocity difference.

[ukrifleman]

It's a lottery to try to match published data with home loads, as there are so may variables to consider.
For instance, different batch of the same powder, different primers, different test barrel, variations in ambient temperature, humidity, barometric pressure etc and finally, different test equipment.
ukrifleman.

[charlie b]

Yep, many variables. Just look at the different load data from different manufacturers.

I do use the maximum velocity number as a measure of how close I am to max. I have found more than once that if I go over the max listed velocity then I will probably experience pressure issues, eg, sticking cases.

[Froogal]

Got a chrono a few months back and started checking my hand loads.
My loads were on average 100 fps faster than the manuals show with unique.
Checked with another chrono and the results were the same.
This is with 38spl,,44spl,44magnum ,45 colt and 45acp.
This is only with unique powder.
But my loads are close to published loads with 2400 and 231.
Anyone else notice higher velocities with unique?

What was the length of the barrel of the gun that was used for testing? And what is the length of the barrel of the gun you are using?

[Larry Gibson]

The variation causing the most FPS change other than expected lot to lot variation in old vs new powders is caused by humidity. Once the canister is opened the powder is subject to that variation. It makes more of a difference than many think.

[willy]

My unique is the 8pound jugs, and was opened about a year ago.
Always stored in a dry basement with the cap screwed on.
This is the only powder I use that gives higher fps than manuals list
2400,,231,,and none of the rifle powders do this!

[TD1886]

The variation causing the most FPS change other than expected lot to lot variation in old vs new powders is caused by humidity. Once the canister is opened the powder is subject to that variation. It makes more of a difference than many think.

Larry and I discussed this in another thread thoroughly. He's correct. I mentioned I had bought an old cardboard can of Unique that had been openned, but not used. I said something about it maybe being "dried out or must drier" then the new stuff I got. Think about it this way, what lights and burns faster, damp wood or dry wood?

[willy]

Larry and I discussed this in another thread thoroughly. He's correct. I mentioned I had bought an old cardboard can of Unique that had been openned, but not used. I said something about it maybe being "dried out or must drier" then the new stuff I got. Think about it this way, what lights and burns faster, damp wood or dry wood?

I understand that …but it has not affected any other powder I have .

[TD1886]

I understand that …but it has not affected any other powder I have .

Well you know how long ago Unique came in the cardboard bottles? Long time. Have you ever heard you should shake your powder that set for a long time?

[Tall]

I was worried when Alliant said they were going to change the Unique formula to be "less dirty". So I stocked up on the Hercules version back in the 1990's. I have several pounds still in the metal cans. Probably a lifetime supply. It's great stuff. There is not one thing I would change.

[Larry Gibson]

I understand that …but it has not affected any other powder I have .

Some types of powders are more susceptible than other types. It's just one of those "variables" that we mostly have little control over. What I do is store my powder in an old commercial refrigerator (no freezer compartment). My reloading is done in my small garage (man cave) with the temperature mostly held at a constant 75 degrees +/-.

The humidity doesn't fluctuate much down here in the desert country. When I lived up north in Washington and Oregon I had numerous top end loads for various cartridges. I began pressure testing when I still lived up there. Those loads pressure and velocity tested just fine. The powder was then stored in a wall locker in my garage up there with no temperature of humidity control. Of course those loads were loaded with the powder exposed to much higher humidity and lower temperatures.

After moving down here to western Arizona I tested those same loads loaded with the same powders out of the same jugs with nothing changed other than a year + in the desert temps and lower humidity. I found dramatic increases in velocity and, in some instance, pressures. Interestingly I found no velocity/pressure change in the hermetically sealed US 7.62, 5.56 and 45 ACP ammo. That's when I put my own powder supply into "climate control" as best i could. After about 6 months the variations due to humidity changes stopped.

Speaking of different effects on different powders humidity can have, I found in the 44 Magnum, the velocity/pressures of 2400 remained pretty consistent between loads up north and down here with the very same powder. However, when the same jug of H4227 was tested the velocity/pressure showed a marked increase. It's just one of those things.......

[popper]

So humidity slows down the burn rate?

[Larry Gibson]

So humidity slows down the burn rate?

Yes. Also if the powder contains moisture from the humidity it is heavier. Ergo, with a charge of 6 gr of Unique that is "humid" you will actually have less powder than with a charge of 6 gr of "dry" powder. That is because the one includes the moisture content in the weight.

[Kosh75287]

A "test", though perhaps an inconvenient one, for checking the brisance of various lots of Unique might be to chronograph the Keith/Skelton .44 Special load with them from a 4" or 6" revolver. If memory serves, 7.5/Unique/245 gr. LSWC clocks at 950 f/s from a 4" N-frame barrel. If the s.d. is + 25 f/s or less, this method might enable the reloader to discern the difference from one production lot to another.

[44MAG#1]

With the plastic containers of today that powder is in, humidity ,in my opinion, NOTICE I said in MY OPINION would be far, far, far, far, less of a concern than when powder was sold in cardboard containers like Hercules used.
Unless one leaves the lid off or doesn't tighten the lid securely
Some act like it is an IMPOSSIBILITY for a screwed up lot of powder to get out.
Maybe not a dangerous lot but still a screwed up lot.
NOTHING is impossible where humans are involved.
If that is hard to believe just look at oneself.

[popper]

I've heard comments on another board about not reloading on high humidty days, could be powder absorbtion OR H2O in the air in the case turning to steam when fired. Expansion of H2O when turning to steam. I consider it a minimal effect for my shooting. But I could be wrong. Flake powder would have greater H2O absortion area than extruded.
edit: expansion ratio of air compared H2O is very small! Conversion to steam can increase pressure by 2.5k psi. Typical H2O/air ratio is 1% at 50% RH!
Interesting.
Conclude that damp powder can retard powder burning and humidity will increase pressure. I assume air moisture can be absorbed by powder in the closed cartridge case. As the heat required to vaporize H2O is much less than that required to vaporize the powder, IMHO the retarded burn rate is minor.
I'm not going to worry about it!

[44MAG#1]

I've heard comments on another board about not reloading on high humidty days, could be powder absorbtion OR H2O in the air in the case turning to steam when fired. Expansion of H2O when turning to steam. I consider it a minimal effect for my shooting. But I could be wrong. Flake powder would have greater H2O absortion area than extruded.

I have never heard of that. We could add that to the list of numerous probable causes of variations in average velocities.

[Tim357]

Yes. Also if the powder contains moisture from the humidity it is heavier. Ergo, with a charge of 6 gr of Unique that is "humid" you will actually have less powder than with a charge of 6 gr of "dry" powder. That is because the one includes the moisture content in the weight.

This is one reason I use volume measures. The powder column will be the same height in the case, regardless of weight