One of the strangest things about the history of smokeless muzzle loading is the way loads have been developed. If one were to consider factory suggestions there would seem to be only three powders that will possibly work, VV N110, Xmr-5744, and Imr-SR4759. (I know SMI and others have different load suggestions but it?s hard to describe them as factories)
Now that does not mean these three are the only three ever suggested many of you may remember AA 2400, and Imr-4227. Still since shooters seem to want what works the three in the first paragraph are the cream of the crop. There are those who?d broaden the list because a week does not go by without a few shooters asking if they can use one powder or another in their smokeless rifle?.
The principle that dictates if a powder will work or not is always the same thing: pressure. Pressure is the one load characteristic that cannot be ignored when choosing a good load or powder for smokeless use.
The reason that there are three preeminent factory powders is that all make the best possible pressure when loaded to the suggested levels. Now there are other smaller reasons for these three successes like granule size, ease of ignition, and availability but if it wasn?t for the fact they all make the right amount of pressure at a usable load level then the other reasons don?t mean much.
In the past e-book chapter I already commented on the maximum pressure I think a smokeless muzzleloader should shoot. I said about 40,000psi would be an upper limit but I didn?t say what should be the lower limit. Perhaps I should because too low a pressure while not dangerous has as much effect otherwise on the load as maximum pressure. Things work such that too low a pressure would be a tougher problem to avoid than too high. Things being the same all around then a lower pressure limit should be about 30,000psi. So now we have established a window of working pressure between 30,000 and 40,000psi.
In the early days of smokeless shooting only a very few people knew the pressures of any given load. One of the early load developers knew that was a problem so he asked me to do something about that. Through experience I could tell him approximations but it was decided that some way to actually measure the loads was the best way to proceed. In a matter of two years actual measurements of different smokeless loads took place.
When we go back to the three popular factory suggested powders it should be noted they all follow what I?ve listed as ideal. They all shoot between 30,000 and 40,000psi when loaded with common weight bullets (250 and 300 grain) at the suggested amount (40 to 45 grains). The question now is, are there other powders that will shoot to the proper pressure window and not be disqualified by some other property?
Below this paragraph you will see a definitive answer. The image is a pressure measurement as made by the RSI ?pressure trace?. Other measurement systems were used (the Oehler model 43 and 83) but this is the easiest one to give as an image. The load was 68 grains of Hodgdon H-4198 power behind a 300 grain SST bullet. This load sounds very different from many others. One thing that seems odd is 68 grains of powder is more than 20 grains past the load level we mentioned for the factory three powders. Even with a need to explain differences one thing remains the same. The peak pressure is between 30,000 and 40,000psi as clearly indicated on the graph.
You may wonder if the powder level is the only difference between the factory load powders and H-4198. There is another difference and that is shown by the curve on the image looking rounded and fat. With so much more powder to burn the pressure peaks at the same level but the time the pressure persists at any given level is much longer. Pressure exerted longer results in more energy and more energy means the bullet goes faster. In this case the bullet goes about 200 to 250fps faster than the 40 to 45 grain loads.
Some wonder why it takes so much powder to reach pressure and the answer is different powders burn at different speeds. The pressure produced in a barrel depends on how much of the solid fuel (powder) is turned to gas. The more gas made the higher the pressure. But there is another factor. That is how fast the fuel is converted from a solid to gas. A slower burning fuel can make more gas but release it over a longer time. The result is more gas to propel the bullet but no change in over all pressure because there is more time.
Have you ever heard the expression ?you don?t get something for nothing?? You don?t get something free in this case either the extra bullet speed comes at the expense of using more fuel and feeling more recoil. But you can notice that the price need not include higher pressure.
So getting a powder to shoot in the pressure window at different levels is not much a big problem there are several to choose from. Still it?s is not as easy to get a total grasp of what is occurring knowing only what we?ve covered so far. The example of H-4198 and a 300 grain bullet is actually an idealized example. Other cases need consideration on their own merit.
Ignoring the above can lead to choosing a load that doesn?t suit the purpose. Let?s try one. Someone told us that H322 will shoot smokeless so we endeavor to pick a load that makes sense. One shooter post on the message board he has shot 75 grains under a 250 grain bullet and we wonder if 75 grains is too much powder. After all, it is 30 grains more than factory suggestions. We see others report it working as well so it seems safe enough that we decide to actually shoot the load
At the range we discover the load shoots safely and targets are showing some good accuracy. So we conclude 75 grains of H322 is great. That is a good conclusion that just happens to be wrong. Look at the following.
Do you see what the peak pressure for 75 grains of H322 under a 250 grain bullet happens to be? It?s so low as to be distorted by the graph resolution. Shooting this low a pressure can cause all kinds of problems despite the range targets showed an accurate conclusion.
What can we do? We can do what is happening in the graph listed below. It was achieved by raising the powder charge to 81 grains. As you see the pressure has risen into our window (though at the bottom of useful pressure) so this must be an ideal load, right? It does shoot well in many rifles and it does fit the pressure range but it has another quality. It shoots the bullet to light speed and the recoil will bring tears to tears to your eyes.
Some think more is better but how dead do deer get? Besides that the pressure is still near the bottom of suggestion and the best loads run in the middle of the road. So it would be best to go to nearly 90 grains. If the load is not made in error there is no chance of an over pressure. But there is considerable chance of head aches, hurt shoulders and a bad case of the flinches.
The above illustrates the possibility of pressure starvation in a 50 caliber rifle. If one had fired any 50 caliber smokeless rifle in a cased round he would probably be prepared for such possibilities. One 50 caliber rifle that gives us some useful ideas is the 50 Alaskan. The rifle was designed for Brown and Polar bear protection and its? lever action does not prevent it from being very good at the task.
The pressure limit for the 50 caliber bear swatter is 35,000CUP. The CUP part of this limit causes a little stumble because we have listed our limit in psi and the two don?t convert in exact manner. However 35,000CUP is likely less than 40,000psi. With that we get a pretty good picture of comparative pressures.
If you shoot the 50 Alaskan to full power you?ll find even with a limited pressure loads easily exceed 4,000fpe with 54 to 62 grains of the proper powder. Things are not a complete comparison because the bullets used in the lever gun are very different fro those shot from a smokeless muzzleloader. But it can be clearly seen you can go a long way on only 40,000psi of pressure.
Now that does not mean these three are the only three ever suggested many of you may remember AA 2400, and Imr-4227. Still since shooters seem to want what works the three in the first paragraph are the cream of the crop. There are those who?d broaden the list because a week does not go by without a few shooters asking if they can use one powder or another in their smokeless rifle?.
The principle that dictates if a powder will work or not is always the same thing: pressure. Pressure is the one load characteristic that cannot be ignored when choosing a good load or powder for smokeless use.
The reason that there are three preeminent factory powders is that all make the best possible pressure when loaded to the suggested levels. Now there are other smaller reasons for these three successes like granule size, ease of ignition, and availability but if it wasn?t for the fact they all make the right amount of pressure at a usable load level then the other reasons don?t mean much.
In the past e-book chapter I already commented on the maximum pressure I think a smokeless muzzleloader should shoot. I said about 40,000psi would be an upper limit but I didn?t say what should be the lower limit. Perhaps I should because too low a pressure while not dangerous has as much effect otherwise on the load as maximum pressure. Things work such that too low a pressure would be a tougher problem to avoid than too high. Things being the same all around then a lower pressure limit should be about 30,000psi. So now we have established a window of working pressure between 30,000 and 40,000psi.
In the early days of smokeless shooting only a very few people knew the pressures of any given load. One of the early load developers knew that was a problem so he asked me to do something about that. Through experience I could tell him approximations but it was decided that some way to actually measure the loads was the best way to proceed. In a matter of two years actual measurements of different smokeless loads took place.
When we go back to the three popular factory suggested powders it should be noted they all follow what I?ve listed as ideal. They all shoot between 30,000 and 40,000psi when loaded with common weight bullets (250 and 300 grain) at the suggested amount (40 to 45 grains). The question now is, are there other powders that will shoot to the proper pressure window and not be disqualified by some other property?
Below this paragraph you will see a definitive answer. The image is a pressure measurement as made by the RSI ?pressure trace?. Other measurement systems were used (the Oehler model 43 and 83) but this is the easiest one to give as an image. The load was 68 grains of Hodgdon H-4198 power behind a 300 grain SST bullet. This load sounds very different from many others. One thing that seems odd is 68 grains of powder is more than 20 grains past the load level we mentioned for the factory three powders. Even with a need to explain differences one thing remains the same. The peak pressure is between 30,000 and 40,000psi as clearly indicated on the graph.
You may wonder if the powder level is the only difference between the factory load powders and H-4198. There is another difference and that is shown by the curve on the image looking rounded and fat. With so much more powder to burn the pressure peaks at the same level but the time the pressure persists at any given level is much longer. Pressure exerted longer results in more energy and more energy means the bullet goes faster. In this case the bullet goes about 200 to 250fps faster than the 40 to 45 grain loads.
Some wonder why it takes so much powder to reach pressure and the answer is different powders burn at different speeds. The pressure produced in a barrel depends on how much of the solid fuel (powder) is turned to gas. The more gas made the higher the pressure. But there is another factor. That is how fast the fuel is converted from a solid to gas. A slower burning fuel can make more gas but release it over a longer time. The result is more gas to propel the bullet but no change in over all pressure because there is more time.
Have you ever heard the expression ?you don?t get something for nothing?? You don?t get something free in this case either the extra bullet speed comes at the expense of using more fuel and feeling more recoil. But you can notice that the price need not include higher pressure.
So getting a powder to shoot in the pressure window at different levels is not much a big problem there are several to choose from. Still it?s is not as easy to get a total grasp of what is occurring knowing only what we?ve covered so far. The example of H-4198 and a 300 grain bullet is actually an idealized example. Other cases need consideration on their own merit.
Ignoring the above can lead to choosing a load that doesn?t suit the purpose. Let?s try one. Someone told us that H322 will shoot smokeless so we endeavor to pick a load that makes sense. One shooter post on the message board he has shot 75 grains under a 250 grain bullet and we wonder if 75 grains is too much powder. After all, it is 30 grains more than factory suggestions. We see others report it working as well so it seems safe enough that we decide to actually shoot the load
At the range we discover the load shoots safely and targets are showing some good accuracy. So we conclude 75 grains of H322 is great. That is a good conclusion that just happens to be wrong. Look at the following.
Do you see what the peak pressure for 75 grains of H322 under a 250 grain bullet happens to be? It?s so low as to be distorted by the graph resolution. Shooting this low a pressure can cause all kinds of problems despite the range targets showed an accurate conclusion.
What can we do? We can do what is happening in the graph listed below. It was achieved by raising the powder charge to 81 grains. As you see the pressure has risen into our window (though at the bottom of useful pressure) so this must be an ideal load, right? It does shoot well in many rifles and it does fit the pressure range but it has another quality. It shoots the bullet to light speed and the recoil will bring tears to tears to your eyes.
Some think more is better but how dead do deer get? Besides that the pressure is still near the bottom of suggestion and the best loads run in the middle of the road. So it would be best to go to nearly 90 grains. If the load is not made in error there is no chance of an over pressure. But there is considerable chance of head aches, hurt shoulders and a bad case of the flinches.
The above illustrates the possibility of pressure starvation in a 50 caliber rifle. If one had fired any 50 caliber smokeless rifle in a cased round he would probably be prepared for such possibilities. One 50 caliber rifle that gives us some useful ideas is the 50 Alaskan. The rifle was designed for Brown and Polar bear protection and its? lever action does not prevent it from being very good at the task.
The pressure limit for the 50 caliber bear swatter is 35,000CUP. The CUP part of this limit causes a little stumble because we have listed our limit in psi and the two don?t convert in exact manner. However 35,000CUP is likely less than 40,000psi. With that we get a pretty good picture of comparative pressures.
If you shoot the 50 Alaskan to full power you?ll find even with a limited pressure loads easily exceed 4,000fpe with 54 to 62 grains of the proper powder. Things are not a complete comparison because the bullets used in the lever gun are very different fro those shot from a smokeless muzzleloader. But it can be clearly seen you can go a long way on only 40,000psi of pressure.
