Black Powder Compression in .45 Colt and Schofield

[wilded]

Can I compress BP in a pistol cartridge too much?

[bigted]

naaaaaaa! you can compress the stuff till there apears a bulg on the case where the powder is compressed as much as its going to be. experimentation is the only way to come to this point just where it almost starts the bulg but not quite. i have done so with 45 colt...38-55...45-70...45-120...and im always surprised when it happens.

when you get almost to the stopping place try this...compress it with only half the powder in the case then put the remainder of the powder in and compress it for a total amount that will be very compressed.

think you will find that your overcompressed charge will be inaccurate tho. powerfull but not so much in the accuracy dept.

good luck and do tell about your outcome...by the by...i loaded 40 grains and tryed it in the model p colt [aftermarket revolver by uberti] and it bounces to say the least when loaded behind a 250 grain boolit.

[JeffinNZ]

There are a lot of myths (or BS) out there about BP compression.

I have never bought into the theory that some BP needs to compressed 'x' amount to make it burn at optimum. Rubbish. It's about getting the right amount of powder under the boolit to find the sweet spot. That's all.

In my .38-303 I load 60gr of Swiss 1.5Fg and compress it .35 inch to fit the boolit in the case. Shoots amazingly well though everywhere I read that Swiss powder does not like being compressed.

Jam as much in as you need to I say.

[w30wcf]

Awhile back I dissected some UMC black powder 45 Colt factory cartridges and found that they had .20" of compression.

w30wcf

[Springfield]

OK, I'm stupid, how can you tell how much a powder was compressed after it happens? Take it out and stir it up until it is it's original consistancy?

[Tom Myers]

OK, I'm stupid, how can you tell how much a powder was compressed after it happens? Take it out and stir it up until it is it's original consistency?

First, determine the seating depth of your bullet.
Next, dump your powder charge into the case and measure the distance from the mouth of the case to the powder level.
Finally, subtract the powder level value from the seating depth to determine the amount of linear compression of the powder.

In my opinion, the amount of linear compression is only of value when applied to a certain powder in an individual case. A more meaningful value would be the percentage of compression of that certain powder.

If you wish to determine the percentage of volume compression, then you will need to calculate the volume of the powder after it has been poured into the case (maybe through a drop tube which will settle the powder and create a powder volume with more density than loose powder).

The volume of the resized, empty case must first be known or determined.
1. To do this, weigh the empty resized case and record that value (in grains) as the "dry weight". Now, fill the empty, resized case with water level with the mouth of the case, weigh the case full of water and record that value in grains as the "wet weight".

2. Subtract the "dry weight" from the "wet weight" to determine the water weight (in grains) in the case.

3. Divide the water weight by 252.89 to determine the cubic inch volume of the case. [1 gram = 1cc of water] [15.43236 grains per gram x 2.54 centimeters per inch cubed]

4. Dump the powder into the case and measure the distance from the top of the case to to powder level. Multiply this distance X (bullet diameter / 2) x (bullet diameter / 2) X 3.1416 (Pi) and subtract this product from the cubic inch volume of your case to arrive at the powder volume in the case.

5. Next calculate the volume of your linear compression operation that was described above. (linear compression X (bullet diameter / 2) squared X 3.1416 (Pi).

6. Finally divide the compression volume by the original powder volume and multiply that product by 100 to determine the percentage of compression.

Hope this helps.

[Dale53]

When I was shooting Black Powder Cartridge Revolver in competition (both score targets and silhouettes) I compressed Goex and Swiss 1/16" and had excellent accuracy. I used the .45 Colt Cartridge, the Lyman 452664 bullet (30/1 lead/tin) sized to .452". I used enough powder to compress 1/16" when seating the bullet. SPG lube worked fine but I mostlly used home made Emmert's (50% Beeswax, 40% Crisco, and 10% Canola Oil. Later, I replaced the canola oil with Anhydrous Lanolin for a longer life lube.

My revolver would shoot 70-75 rounds before starting to tie up from fouling. YMMV... My revolver is a Ruger Bisley Vaquero 5½". Clean up took maybe 10 minutes using Friendship Speed Juice then drying and applying Ed's Red.

I was VERY competitive with this combination.

Dale53

[Tom Myers]

OK, I'm stupid, how can you tell how much a powder was compressed after it happens? Take it out and stir it up until it is it's original consistency?

Springfield,

I just re-read your post and it dawned on me that you were asking how to determine the amount of compression used in the original Black Powder loadings.

I really have no good answer to that.

I suppose one could assume that loose Black Powder density is usually quite close to the density of water.

So one could extract and weigh the powder charge then divide by 252.89 to arrive at the original volume in cubic inches.

I have found that settling black powder with a drop tube or vibrating will generally reduce the volume by amounts varying between 9-12% so just say 10%

Further assuming that the 45/70 case full of black powder would hold 70 grains of powder.

So drop tubing 70 grains of black powder into a 45/70 case should produce an in-case volume of 70 / 252.89 - (70 / 252.89 * 0.10) = 0.24912 ci in the case that has a volume of 0.27680 ci.
So 0.27680 - 0.24912 = 0.02768 cu in of space in the top of the case.
This would place the powder level at 0.02768 / (0.458 / 2)squared / Pi = 0.168 inches below the top of the case.
Now if the bullet is seated to a depth of 0.5 inches, then the linear compression of the powder would be 0.5 - 0.168 = 0.332 inches of compression (Which, incidentally, I have found works quite well in my 45/70 with Goex FFG powder)

To find the volume percentage of compression, calculate the volume of the 0.332 inches [0.322 * (458 / 2)squared * 3.1416{Pi}] = 0.05469 ci .

Divide the compression volume by the settled volume and multiply by 100 to determine the percentage of compression.
0.05469 / 0.24912 * 100 = 21.95% powder compression

Substituting the value of the weighed charge in place of the 70 grain value should produce acceptable results.

[w30wcf]

OK, I'm stupid, how can you tell how much a powder was compressed after it happens? Take it out and stir it up until it is it's original consistancy?

Springfield,
After dissecting the cartridge, I put the powder back into the case. I then took the bullet which I made undersized enough that it would slip easily into the case, and placed it on top of the powder. The oal measurement was 1.78" less the cartridge oal of 1.58" = .20" compression.

Tom,
Thank you for your information.

w30wcf

[John Boy]

I have never bought into the theory that some BP needs to compressed 'x' amount to make it burn at optimum. Rubbish.

NOPE!

In my opinion, the amount of linear compression is only of value when applied to a certain powder in an individual case. A more meaningful value would be the percentage of compression of that certain powder.

Tom is absolutely correct ...

the Black Powder Cartridge News -2009 Fall - "Some Black Powder Compression Data" article by Bob Woodfill:
Caliber - 45-70
Lyman 457124
Constant volume of FFg powder used
Compression tested: 0" - 1/8" - 1/4" - 3/8" and 1/2"
Best 3 Shot Groups 100yds ... 5 shot groups were tested also, with the same compression values except for Goex (1/4") and Schuetzen (1/2")
Goex - 0.62" with 1/8" compression
Goex Express - 0.26" with 1/4" compression
Schuetzen - 0.61" with 1/4" compression
Swiss - 0.56" with 1/2" compression
KIK - 0.65" with 0" compression

Note that each of these 3 shot groups were less than MOA!
PS: Tom Woodfill is a top ranked BPCR match shooter

[John Boy]

Now, let's discuss WHY different powders like different compressions? The answer can be summarized ... What's in the Can ...
* comprising potassium nitrate, sulfur, charcoal
* the processing by each vendor
* the density of the grains
* the sieve ratio of the grades
* and the final moisture percentage of the powder

So ... who wants to lead off and be First ... filling in the WHY details for each dot point ? And let's see who goes to the Head of the Class!

Here's a starter hint ... wood used for charcoal: can be Swamp Maple, Buckthorn and Alder Buckthron. Name what vendor uses which wood and why the charcoal is important to compression?

[Grapeshot]

Can I compress BP in a pistol cartridge too much?

Only if it detonates in the press. Seriously, I loaded a batch of .45 Colt with a WEIGHED charge of 40 grains of 2Fg Goex dropped through a drop tube into Winchester Cases.

I then used a card wad cut from Soda can cartons and compressed the powder with a compression die so I could seat a .454 Big Lube 250 grain boolit on top of the powder and set it off with a CCI 350 Large Pistol Magnum Primer.

Recoil was stiff and the concussion was intense. Have fun and be safe.

[Dale53]

There are other considerations, also. When I shoot black powder in my .45 Colt revolver, I use a rather soft bullet (30/1 lead/tin Lyman 452664). By compressing it 1/16", that's enough to be certain the case is full and it shoots with excellent accuracy. Most important, however, I do not distort the bullet with the minimal 1/16" seating.

I do not use a compression die with my revolver loads (I do with my minute of angle BPCR loads) as the accuracy demands do not warrant it. Anything under 2" at 25 yards meets my needs with black powder. My revolver actually will shoot 1½" at 25 yards with my black powder loads using Goex, Swiss, and Pyrodex. If you try to use the bullet (when seating) to compress the powder you will almost certainly damage it losing accuracy. Further, I wish to spend my time shooting, not fooling with drop tubes, compression dies, and such. If I had to do it to get the accuracy I demand, then I might consider it. However, I don't and I do not...

FWIW
Dale53