>> Black Powder, Pressure And Effects :: By Bill Marney Sr. (Hilljack) on 2005-07-16
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BLACK POWDER PRESSURE AND EFFECTS
Please remember that this is for general use and is not a treatise or Doctoral paper, it is meant for the average person to use. And the information has been gleaned from books and experience in life and shooting BP. They are guidelines not Gospel, look, read, and make the decisions from your own experiences. Go out and have some fun and learn!!
The use of different powder through out the ages has caused many an argument. But the main point is to use common sense when shooting and handling BP weapons. The old school would say that with a 50
and larger use 2F and below that point use 3F. I have used 3F in my rifles up to 62
for the last few years with no ill effects, in fact in my opinion, the 3F burns cleaner and has given me better accuracy across the board. Remember this is just a grading size, now to throw some more information into the fire, so to speak. There are basically 3 grades of powder along with the granulation differences, Musket which is the slowest, Rifle which is mid road and sporting which is the hottest. These will be brought up later. And here again you will hear me say this…Read your patches and see what your rifle is doing, and make the necessary changes. What happens with the finer powder is that you actually get more powder physically in the barrel. It has more total surface area, which can lead to better flame and combustion propagation, and the speed will increase to a certain point and then begin to slow down due to the extreme increase in Total Surface Area. The pressure spike will be more pointed in that the pressure will peak higher and earlier in the ignition cycle, this can cause some really big problems, because along with this comes heat.
Gas cutting and using high charges has been in controversy for many years, with many different camps on the subject, these are my views and thoughts. Just like with any subject there will be varying differences in both the writer and how he presents the information. And this will influence people directly.
First metal, liquids and gases all act differently under pressure than when not confined. Take water, put it under pressure and you increase the boiling point and also the amount of heat it can carry. Metals will and do act the similar manner. Erosion/Cutting occurs when you have gases under pressure escaping to a lesser atmosphere or meets a obstacle in the flow path and creates a low pressure area and move through the break. When you are dealing with a expanding gas in a confined space that grows and creates enough pressure to move the object (Ball and patch) you don't really have any of the criteria. The only place I know that this occurs is the vent or nipple area where you are venting hot gases.
You can cut a barrel, just as bad, and probably faster than you would believe by not having a good patch and ball combination and setting up these small pathways, this is why it is necessary to read the patches and see what your rifle or pistol is telling you...
Resistance to movement creates heat and pressure, so if you try and push a 45
ball with 80 Grains of 3F in a 1-48" would give you a certain resistance (Pressure/Temperature). Now do the same in a 1-72" twist, your resistance to movement is much less meaning less pressure and heat. And as bore size increases the twist slows down accordingly. And powder consumption goes up to be able to develop the correct amount of spin that is required to stabilize the ball. And even though they may have the same twist, they may not use the same load...
Now the purity of the fuel/ingredients will dictate the ratio of efficiency, and that is a long one on it's own. That’s where one powder you will use 60 Grains and the next you will use 80 grains to accomplish the same task. Or as the twist is slower the more powder is required to get it to perform satisfactorily. There are no standards, to my knowledge that are abided by as to granulation, look at the difference between Chinese and Swiss Powders. The way they are polished and finished will make a difference in the performance. Just like in a gas engine you can loose power by having a poor fuel/air mixture. Either too much or too little and performance suffers. When you have too much you foul out or have excessive fouling, telling you to back off. I can go 30 to 50 shots with out wiping the bore and hold good accuracy or if you want, you may wipe after every shot. What works for you. What ever is your comfort zone.
This is not an exacting science. The British used Forsythe rifling (Very slow 1-72" to 1-144") and big charges with no ill effects. Rules of thumb are just that a guideline, but you must take care of your equipment and know what it is doing. I have shot these loads from my rifle for over 5 years, since I built it, and there is no cutting or erosion and I have unbreeched it several times. Remember I have been using Musket Burn rate, not rifle or sporting grade powders. I use Patent Breeches in all but a couple of my rifle that I have built, but I doubt that makes any difference.
The charge of 120 Grains of 3F (Elephant, GOEX, Wano, which are basically Musket powders) with my 58 or 62 Cal (1-72”) puts me about 2" high at 100 yards, so when I'm hunting, and I have full confidence that anything from 125 yard down is within my range...This is only a simple view...
Well, thanks for reading my thoughts and opinions....
Bill Marney Sr. (Hilljack)
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