4F Black Powder Question
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The reason it is so hotly debated, is the same as with other questions of the day. It is because it is logic vs. emotion. Facts, figures, experience and experiments, vs. fear, anger. passion and shame.
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I haven’t seen much evidence for regular chronograph use among the forum’s posters. Doesn’t mean it doesn’t exist but... be that as it may, you’re describing a sound approach.
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I would
I would not be afraid to shamelessly mix the 4f with 3f passionately and be angry if i ran out of priming powder later.
RAEDWALD
40 Cal.
The core fact is that the smaller the grain the faster and higher is the peak pressure. How much that will affect the safety of the gun is a matter of debate. It is simply a risk that is avoidable without affecting the use of the gun. How big that risk may be is uncertain in the individual case.
I have acquired a 0,320" Ardesa Crockett rifle. The twist at 1:48 allows for a patched ball to use an accurate load as light as one desires. With a conical the twist needs a much larger load to get the same revolutions per second for the same stability. Even with a large load in such a small bore I judge that it should manage the extra peak pressure to obturate the short bullet and exit it at a suitable high velocity were I to use 4F powder. I would be concerned (my judgement) in a larger bore that extra pressure and faster pressure rise is not so containable. Others may judge differently.
I have read extensively on the enormous amount of research done by governments, manufacturer and academics on the analogous work on heavy artillery in the latter 19th century and they had catastrophic problems working with ordinary coarse grained black powder. These were solved with a huge improvement in performance by swapping to very large fist sized blocks of back powder and even more with the even slower burning brown/cocoa powders using partially carbonised charcoals. How analogous that may actually be to small arms is open to question but it demonstrates a hazard. Whether that hazard is an actual risk I am not qualified to argue.
You are all, I trust, intelligent rational adults so must make up your own minds but I would be lacking in my duty to others if I did not make my concerns known. I think the hazard exists. I think the risk is small. But I do think the risk is proportional to the bore with a normal charge. No one is obliged to agree with me.
I have acquired a 0,320" Ardesa Crockett rifle. The twist at 1:48 allows for a patched ball to use an accurate load as light as one desires. With a conical the twist needs a much larger load to get the same revolutions per second for the same stability. Even with a large load in such a small bore I judge that it should manage the extra peak pressure to obturate the short bullet and exit it at a suitable high velocity were I to use 4F powder. I would be concerned (my judgement) in a larger bore that extra pressure and faster pressure rise is not so containable. Others may judge differently.
I have read extensively on the enormous amount of research done by governments, manufacturer and academics on the analogous work on heavy artillery in the latter 19th century and they had catastrophic problems working with ordinary coarse grained black powder. These were solved with a huge improvement in performance by swapping to very large fist sized blocks of back powder and even more with the even slower burning brown/cocoa powders using partially carbonised charcoals. How analogous that may actually be to small arms is open to question but it demonstrates a hazard. Whether that hazard is an actual risk I am not qualified to argue.
You are all, I trust, intelligent rational adults so must make up your own minds but I would be lacking in my duty to others if I did not make my concerns known. I think the hazard exists. I think the risk is small. But I do think the risk is proportional to the bore with a normal charge. No one is obliged to agree with me.
The smaller the bore the higher the pressure and for longer than a larger bore
In a smaller bore the surface area for the propellant to act on demands more work and for longer which often translates in much higher muzzle velocity than a larger bore.
Basic principles of hydraulic systems can demonstrate this.
In a larger bore the propellant has more surface area. It is there for easier to lift off. That coupled with quickly developing volume increase actually drops or holds pressure peaks low and short.
This is easily demonstrated by nitro powder charts and applications to shotguns. Much slower or retarded powder is needed for a 20g compared to quite fast powders for a 12g.
Whilst there is no direct comparison with black powder and nitro the underlying physics of a smaller piston arrangement compared to a larger piston arrangement is that the lesser will need more pressure to return any work.
So in small arms, not cannon or artillery, no relationship what so ever, it matters not it being a fine granulation. We know this because it is not banned from such use. It is not banned from such use because no one has demonstrated it causes damage or is dangerous.
Assuming proves nothing. I use to ride motorcycles with a gas tank next to the families jewels. Not once did I contemplate them getting flamed so thought that putting diesel fuel in the tank would be safer!
My own personal tests with 1f in shotguns resulted in lousy patterns and very low velocity. In numerous guns I had to tip far more in than the volume of the shot load to get some velocity but the patterns were lousy. This was with 12&.75". 20g was slightly better but not enough for me to recommend it.
Nope 3&4f for me all day long thanks.
B.
Here is a way to tell anyone with enough money can buy it and try the different powders and sizes.
https://www.shootingsoftware.com/mm5/merchant.mvc?Screen=CTGY&Store_Code=RSI&Category_Code=PTThat will settle it.
https://www.shootingsoftware.com/mm5/merchant.mvc?Screen=CTGY&Store_Code=RSI&Category_Code=PTThat will settle it.
Settle what please?
That it don't blow up barrels and harm people?
We already know this. No?
Settle what actual pressure is, that what for those who have to see figures.
Well I guess it's only my opinion but I reason that the barrel makers have already tested it and found it well within limits otherwise we would know about it!
And that is assuming. I am not arguing about it as I also use 4fg for more than priming. A simple test with the tool I linked to Would solve any arguments.
The guys at the club I belong to were using one of these they had borrowed from someone to develop loads for ‘muzzleloaders that don’t smoke’ a couple of years ago. Never checked anything I was shooting, as I don’t play that close to any dangerous cliff. Personally had team that used to work for me use this type of technology for evaluating pressure regulating valves. Very repeatable. Personally, wouldn’t spend the money on it for our sport. A lot of other things to buy first.
Kind of why I don't have one 
Too emotional of a topic for some to ever change their mindset with data. It would never be enough. I know guys (or did know guys) that can go on for hours about the medical benefits of smoking tobacco products and others that will argue the dangers of using seatbelts.
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But only field testing for a couple hundred years....... final report is apparently not in yet.
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So how many here know what the pressure figures for their pet 3f or 2f loads are?
And if you don't have a figure how do you know it is safe?
And if you don't have a figure how do you know it is safe?
Because everyone says so and they all know what's best!
The powder load testers are only good for a static peak pressure. To get the real difference in granulation pressures you would need dozens of testers spaced down the barrel length.
Where the powder testers work And I use a version of, is total volume expansion of gasses.
I use a 4" mortar tube with a close fitting light "slug" By using VERY SMALL amounts so as not to actually launch the slug I can tell if the differences in charcoal, oxidizer, proportion etc of different lift powders. I will use an electric ignition of 2 or 3 CC by volume of the powder and see how far up the tube the slug goes before gravity overcomes pressure. Not a scientific grade test device by any means but I can definitely compare my different formulations to each other.
Where the powder testers work And I use a version of, is total volume expansion of gasses.
I use a 4" mortar tube with a close fitting light "slug" By using VERY SMALL amounts so as not to actually launch the slug I can tell if the differences in charcoal, oxidizer, proportion etc of different lift powders. I will use an electric ignition of 2 or 3 CC by volume of the powder and see how far up the tube the slug goes before gravity overcomes pressure. Not a scientific grade test device by any means but I can definitely compare my different formulations to each other.
Nothing published just my own observations and deductive reasoning. If the pressure starts to reduce before the projectile leaves the barrel then drag takes over, slowing the projectile and losing velocity will effect accuracy. So then say you just increase the load to keep the velocity up, then you will get a larger volume pushing out behind the projectile after it leaves the barrel. Fluid dynamics proves that those gasses will expand in a swirl pattern behind, around and in front of the projectile since they have less mass. That effects the accuracy just like a cross wind would except in a random pattern, not the easily compensated wind-age calculations.
Most of my observations come from Pyro work. Watching a 3 or 4 inch festival ball coming out of the tube in slow motion you can definitely see the wobble created by the "puff" after the ball leaves the tube. Bullets are smaller and more dense, but that just means the effects are less not eliminated.
Bottom line 4f isn't the best for targeting with a .50cal long gun... but if it's all you got... It still goes bang and with a little extra luck it will still put meat on the table.
I say, "Save your money. Don't buy it."
In order to get an accurate pressure reading with strain guage testing, they must be mounted on a barrel with tightly controlled, known diameters, machined in the area that is going to be tested.
The guages work by measuring the amount of linear movement or expansion the material has when the pressure is applied and a thin wall tube will move considerably more than a thick walled tube when the same pressure is applied to it. That is the reason the exact size of the barrel in the area of the test needs to be known.
Would one of these give a reading when the gun fires? Yes it would but, without knowing the exact crossectional area of the barrel, where the strain guage is mounted, the answer would be meaningless.
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