calculating black powder loads?

Discussion in 'Black Powder Shooting / Muzzleloaders / Handguns' started by lansdale, Apr 8, 2011.

  1. lansdale

    lansdale New Member

    Apr 8, 2011
    hi everybody,

    i was just wondering, is it possible to calculate black powder loads for a certain rifle?

    i own a 1874 swedish rolling block.
    it has a .58 caliber straight rifled barrel, with a 28 gauge chamber.

    on Tom Bullocks site if found that a 28 gauge black powder shotgun cartridge usually has 55 grains of 2FG powder, and 3/4 Oz of lead shot (which is 328 grains).

    so if this ratio of 55 grains powder for 328 grains of shot is right, could i use this ratio to calculate the amount of powder needed for a heavier shot load?

    lets say (in theory) i'd want to use a shot load of 1 Oz (437 grains).

    (55 grains / 328 grains) * 437 grains = 73 grains of powder

    i know about the "equal volume loads" principle they use with black powder shotguns.

    so i tried to check the calculation i made above, by calculating the volume of blackpowder and the volume of the shot.

    235 grains of 2FG blackpowder = 1 cubic inch,
    so 73 grains of 2FG blackpowder is (1 / 235) * 73 = 0.3106 cubic inch

    lead has a density of 2868 grains per cubic inch
    so 0.3106 cubic inch * 2868 grains = 890.8 grains of lead.
    because 1 cubic inch of lead shot consists of 1/2 lead and 1/2 of empty space, the weight of 0,3106 cubic inch of lead shot would only be half of the 890.8 grains.

    this would mean 445 grains of lead shot with 73 grains of powder when calculated with the "equal volume loads" principle.

    with the "ratio" calculation i calculated 437 grains of lead shot with 73 grains of powder. a difference of 8 grains which is about 1.8%

    some of you (maybe all of you) probably ask "why would you want to calculate something like that?"

    well the thing is where i live it's nearly impossible to find 28 gauge blackpowder cartridges, and we are only allowed to buy and use them if we join a skeet club. to use the rolling block at my usual shooting club i would need to load brass shotgun shells with .58 cast bullets, which ofcourse are almost always a lot heavier than 328 grains. to do that i would need load data...which i cant find anywhere.

    so my question at the end is, could someone give me advice about these calculations? i'd use them as a maximum load and load my cartridges a little lighter to be on the safe side.
  2. TUCO-the-ratt

    TUCO-the-ratt New Member

    Mar 14, 2011
    ALL Black powder cartridges must be loaded so as to have absolutely no air gap under the bullet/shot and generally should have at least some compression on the powder charge.

    I know this sounds suicidal to anyone used to loading smokeless but the rules are all different for black powder.

    Here's a link to black powder cartridge loading

  3. Hawg

    Hawg Well-Known Member

    Mar 23, 2011
    You don't need all the calculations. Use an equal amount of shot to powder in shotshells. Less powder than shot for a tighter pattern and more powder than shot for a wider pattern. For cartridges fill the case to 1/16 of top and seat bullet of your choice. if you want a lighter load use cornmeal for a filler. Never load bp with an air gap, it must be compressed.
  4. lansdale

    lansdale New Member

    Apr 8, 2011
    so does that mean the amount of bp doesnt make the rifle blow up?

    i knew air space between the powder and bullet is lethal, but i thought the amount of powder was important too when in comes to not blowing up the rifle?
  5. myfriendis410

    myfriendis410 Member

    Mar 30, 2011
    Lompoc California
    Black powder doesn't burn; it explodes. It does so at a fixed velocity and a peak pressure which is way lower than progressive burning smokeless powder. Excess black powder will just spew out the muzzle. The oldtimers with their muzzleloaders would start with a patched round ball and around 50 gr. of powder and shoot in the snow while increasing the charge by five grain increments until powder started speckling the snow in front of them. That would be a max charge.
  6. ofitg

    ofitg Active Member

    Feb 25, 2010
    lansdale, your description left me wondering - according to what I have read, the Swedish rolling block was originally chambered for the 12.17x44R rimfire cartridge.... but the book Cartridges for Collectors vol.4 states that they were later converted to centerfire. This book also lists the bullet diameter as .528 inches. Are you certain that your bore is .58 caliber?
    Last edited: Apr 8, 2011
  7. lansdale

    lansdale New Member

    Apr 8, 2011
    when i bought the rifle i wanted to make sure about the exact bore diameter so i made a casting of the camber and the first 2 inches of the barrel, and i did slug the bore with an oversized lead ball.

    the diameter measured between the grooves varies between 0.5799 and 0.5838

    the diameter measured between the lands varies between 0.5530 and 0.5570

    the barrel is marked 1870 while the action is marked 1874.
    i didnt really understand it either. i read about .58 caliber rolling blocks, and 12.7 rolling blocks, but i couldnt find info about one with .58 barrel with a 28 gauge chamber

    oh and ofcourse thanks to everyone for replying, i really didnt know about the amount of blackpowder that could be used. i do remember the "dont leave any space between bullet/shot and the powder" my granddad always said
  8. ofitg

    ofitg Active Member

    Feb 25, 2010
    lansdale, I found the following load data for 12.17x44R in the book, Cartridges of the World -

    Bullet 345 grains ..... Powder 76 grains Fg .... Muzzle Vel 1300 ft/sec

    If I were doing it, I would probably start off with 50 grains of powder out of respect for the gun's age, and fill up any empty case volume with an inert filler like cornmeal.

    If I may ask, what are the chamber dimensions, based upon your chamber cast?
    Last edited: Apr 9, 2011
  9. lansdale

    lansdale New Member

    Apr 8, 2011
    base diameter is about .626
    diameter at the end of the chamber, at 65mm, is about .614

    the rifling starts almost immediately, like in a normal rifle. not a long cone like shotguns usually have.

    the barrel has 8 grooves and 8 lands
  10. ofitg

    ofitg Active Member

    Feb 25, 2010
    I can see why you refer to it as a 28 gauge chamber - your measurements are practically an exact match for the dimensions at

    The book Cartridges for Collectors vol.1 lists a couple of .58 rounds which were ostensibly based upon 28 ga brass hulls - I am attaching the illustrations below.

    Unfortunately, both of these cartridges appear to be too fat to fit into your chamber.

    I don't have any 28 ga brass or .58 bullets to play with - I am wondering if you might have some difficulty getting the .58 projectile to seat down into the 28 ga hull?

    Attached Files:

  11. lansdale

    lansdale New Member

    Apr 8, 2011
    thanks for the info, it tried looking up all sort of old ammo on the internet but didnt see these two.

    according to 28 gauge magtech brass shells have an inside diameter of approx .585

    i'll have to order a box of them as soon as i get 28 gauge shells and .58 bullets registered on my license (thats how it has to be done in my country, it's a pita) to check if and how .58 bullets fit.

    depending on how loose they are i could probably paper patch them if they're a bit loose. i think that would be better than using a crimp each time.
  12. ofitg

    ofitg Active Member

    Feb 25, 2010
    It seems odd that the 15x40R and 15x49R cartridges are slightly too fat to fit into a standard 28 ga chamber.... perhaps the 28 ga chambers were more "generous" back in the 1800s, and your rifle was converted sometime later when the shotshell specifications had been tightened up a bit (?)

    It sounds like you have an interesting project there. If you have access to the Lyman Blackpowder Handbook, it can provide a wealth of ballistic/loading data.

    Getting back to your original question, I might offer the following observations -

    With everything else (bullet weight, bore size, etc) held constant, increasing the powder charge will increase pressures.
    With everything else (powder charge, bore size, etc) held constant, increasing the bullet weight will increase pressures.

    Here are four loads from the ".58 caliber" section of the Lyman Blackpowder Handbook -

    Round Ball (260 gr) .... Powder 50 gr FFg .... Pressure 2960 LUP .... Velocity 863 ft/sec

    Round Ball (260 gr) .... Powder 90 gr FFg .... Pressure 5370 LUP .... Velocity 1162 ft/sec

    570 gr Minie #57730 .... Powder 50 gr FFg .... Pressure 3780 LUP .... Velocity 729 ft/sec

    570 gr Minie #57730 .... Powder 90 gr FFg .... Pressure 9710 LUP .... Velocity 1001 ft/sec

    I would note that ".58" military cartridges such as the U.S. .58 Musket (Berdan) and the British .577 Snider used bullets weighing about 480 gr with powder charges in the neighborhood of 70-80 gr. Those rifles generated quite a bit of recoil, perhaps more than you would enjoy for recreational purposes.

    Please keep us posted on your project!
  13. ElvinWarrior

    ElvinWarrior New Member

    Mountain man method...

    Put the ball or lay the conical down in the palm of your hand...

    Carefully pour BP onto the ball, or conical, until a nice little cone of powder completely covers the lead, but just barely...

    This is a good, off the cuff, way of measuring the powder, it is self regulating, in that the size of the lead, adjusts the amount of powder.

    I tested this many times when I was younger, carefully pouring out the powder, and carefully transferring it into a gradiated powder measure to see where the grainage came out... Damn near right on EVERY TIME !!!!

    Always remember the "KISS" method guys, "Keep It Simple Stupid". Back in the old days, or even today if you decide to go up Alaska way and homestead 20 Acres, being a mountain man, (Ya, you can STILL HOMESTEAD in a few very remote places !!!) They didn't carry around with them a 20lb bag of possibles, or fancy brass measures or any kind of St. Louis Sissy banjangles like that at all... they lived in the dirt and grit by their wits and know how... THINK !!!)



    ElvinWarrior... aka... David, "EW"
    Last edited: Apr 15, 2011
  14. Hawg

    Hawg Well-Known Member

    Mar 23, 2011
    Actually mountain men did use measures. Usually a piece of antler hollowed out to hold the correct ammount but some used fancy bought measures. Some powder horns of the day had built in measures. Some used a hollow horn plug as a measure. Most tailored their loads for the game they were after and used several different powder charges so a couple or three measures were a must have.
  15. acough2001

    acough2001 New Member

    Oct 3, 2013
    Franklin, MA
    I recently bought a Kirst Konverter for my '51 Colt Navy (Pietta). The website recommends .38 Long Colt blackpowder ammo , and I was able to find a dealer who both had it in stock and would ship to my state (MA). After I expend these rounds, I intend to have them reloaded, using pyrodex P instead of BP but using the same type bullet. My question is in regard to the charge of powder needed. If anyone has done this, I'd be grateful for whatever info you can supply.
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