Since reloading centerfire cartridges with black powder requires essentially the same volume of black powder or bp substitute for any particular cartridge/bullet/powder type, I assume the velocity of a given bullet weight/powder type is a given (plus or minus a small amount) for each typical barrel length. What is the typical velocity for a 255gr lswc in a 45colt using triple seven? I shoot a Vaquero with a 4-5/8" barrel, and I'm wondering what velocity I can expect with triple seven, or some other powder type. I'm sure there is a range dependent on exactly how much you compress, and whether you use a drop tube for denser powder fill, or simply scoop it in, but a good average would be helpful. I also assume going with a different crimp groove (if available on a particular bullet) will give you an option in velocity due to the difference in available case space.
While I'm asking, what about a 45-70 black powder load for a 405gr lead bullet? Life must have been much easier when each cartridge produced one or two basic loads with the variation being only the bullet weight and the velocity that bullet achieved when the case was filled to the correct level for that projectile.
Howdy Again
It would be nice if life was that simple, wouldn't it?
You may recall in my earlier post I mentioned that not all brands of Black Powder weigh the same, some are denser than others. Guess what? They burn at slightly different rates too.
Black Powder is not like Smokeless. When Alliant brews up a new batch of Unique, they pull out the secret formula for it and do their utmost to duplicate it exactly, so that this year's Unique performs the same as the stuff they made five years ago. Yes, they may make a minor change every once in a while, but the effort is made to duplicate the performance of the powder from year to year, so reloaders don't get in trouble with outdated data.
Black Powder is not quite the same. Over the years, the specific formulas for Black Powder have varied, from country to country and from year to year. Proportions of the actual ingredients; potassium nitrate (saltpeter), charcoal, and sulfur have varied. By about 1781 the British standardized the formula as 75% saltpeter, 15% charcoal, and 10% sulfur. The US later adopted this as the standard for all powder purchased by the Army.
However some differences still existed in the way the powder was processed.
Today, the manufacturers of Black Powder each put their own 'stamp' on their powder. Some use charcoal from different species of trees and some use charcoal that is prepared differently. Some may vary the graphite coating on the grains. Some may use a slightly different method to screen the grains for size.
The result is that not all modern made Blackpowder weighs the same, and they don't all burn the same either.
OK, now for some hard data. The only time I had a chance to chronograph my own loads, I got an average of 704 fps with a 250 grain lead round nose flat point bullet on top of 31.3 grains of Goex FFg out of the barrel of 7 1/2" Ruger Vaquero. This was a full case of powder with about 1/16" of compression. Remember I mentioned, that modern cases do not have as much case capacity as the old balloon head cases. The same day I clocked my 44-40 rounds out of the barrel of my 24" Uberti replica 1873. It averaged 1015 fps with a 200 grain lead round nose flat point bullet on top of the same 31.3 grains of Goex FFg.
For some more detailed data, let's turn to Mike Venturino's Shooting Colt Single Actions. Mike tested Goex FFg, Goex FFFg, Elephant FFg, Elephant FFFg, and Pyrodex P in 45 Colt. He shot all loads from a 7 1/2" barreled Colt. Bullets were 250 grain lead round nosed bullets.
Powder------------Charge----------Velocity
Goex FFg----------35.0 grains------922 fps
Goex FFFg---------35.0 grains------973 fps
Elephant FFg------36.0 grains-------760 fps
Elephant FFFg-----36.0 grains-------853 fps
Pyrodex P---------25.0 grains-------954 fps
I have left off the variation because I am getting tired of typing.
That is no typo with the Pyrodex weight, Pyrodex weighs a whole lot less than real Black Powder, but it is formulated to give about the same energy as Black Powder by volume. That also accounts for the slight difference of charges with Goex and Elephant. Notice too that by changing from FFg to FFFg it is typical to get a higher velocity out of the same powder charge. Usually between 60-100 fps faster.
Now let's look at 45-70. I have never chronographed my own 45-70 loads, but let's turn to Mike again, this time in his book, Shooting Buffalo Rifles of the Old West.
Mike does not have data for a 405 grain bullet, the closest he comes is 420 grains. He tested Goex FFg, Goex Cartridge, Swiss 1 1/2 F, Elephant FFg, and Wano FFg. All charges were 63 grains. A .060 card wad was used between the powder and the bullets. The test gun was a Shiloh Sharps with a 30" barrel.
Powder
Goex FFg-----------1260 fps
Goex Cartridge----1253 fps
Swiss 1 1/2 F------1290 fps
Elephant FFg-------1163 fps
Wano FFg----------1187 fps
Again, for my tired fingers I have left off the variation, but I will tell you the best was the Goex Cartridge load with a variation of 12 fps. The worst was the Wano load with a variation of 36 fps.
This is the type of data the BPCR guys are interested in. My experience with Black Powder is mostly in cowboy shooting, and we are not terribly concerned with velocity and variation. The BPCR guys are very concerned with it and will experiment with many combinations of bullets, powder, wads, and compression before they are happy.
I can assure you there was the same type of variation of velocity with 19th Century powders and loads. For one thing, there were a whole lot more manufacturers of powder back then and quality varied widely.
Finally, I have no experience with triple seven myself, but if you visit their website you will see that it is approximately 15% more powerful than real Black Powder. So your 777 loads will be a bit hotter than the data shown here. And it does not matter much what shape bullet you use. The weight is what is important. Your comment about the location of the crimp groove is correct. The position of the crimp groove dictates how far the bullet extends into the case, and this in turn dictates the internal volume of the case. If you followed my post with photos showing how to determine the powder capacity with a specific bullet, this becomes obvious.
