7mm Allen Mag test rifle finished.....
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7Rumloader
Well-Known Member
Re: wc872 burn rate
b1g b0re I don't intend upon debating powder burn rates and mathmatical equations but here are some facts.
#1 Yes H-50 BMG is listed as slower than H-870.
#2 WC872 is stated as being able to use H-870 data and AA8700 but My top end load for H-50 BMG was 100 grains behind either a 168 SMK or a 169.5 wildcat and on hot days ( above 85 ) will show pessure ( developed that load during the cold months ). So far I'm up to 102 grains of WC872 with the same bullets and have reached the <u> <font color="red"> </font> same velocity </u> <font color="blue"> </font> as H-50 BMG but have not gotten any pressure signs what so ever! I intend upon going up with the powder once again to wherever I get the best results or pressure signs. This tells me it burns slower than H-870, AA8700, and H-50 BMG powder since I have exceeded the previous load data for each powder by 2 full grains already.
#3 Kirby and jwp 475 also found the WC872 to be a slower burning powder in their tests by exceeding H-870 load data by a good margin along with H-50 BMG data as well.
#4 As far as barrel heat I have not used any hi tech device to measure it but when you can feel a difference by grabbing the barrel after 3 shots of the same bullets only different powder then there must be a difference. True I have not reached max level of WC872 yet and when I do there may be no noticable barrel heat difference at all and when I get there I will say I found no noticable difference in barrel heat at max loads for each powder. Right now it's a night and day difference between the 2 after 3 shots The BMG I assure you that you will turn it loose shortly after grabbing it and the WC872 you can hold with no pain or teeth gritting for as long as you want.
Like I said I don't want to argue mathmatics because I hated frieking equations and formula's in school and I don't like them any better now.
I'm only stating facts that I have so far and when I get more data collected on this subject I will share it over on a thread of mine in equipment reviews titled Wildcat bullets consistency and accuracy.
I'm through hijacking Kirby's wonderful thread about his new Allen Mag.
Sorry for the Hijack Kirby, Len, Dave, Ian ! /ubbthreads/images/graemlins/frown.gif
b1g b0re I don't intend upon debating powder burn rates and mathmatical equations but here are some facts.
#1 Yes H-50 BMG is listed as slower than H-870.
#2 WC872 is stated as being able to use H-870 data and AA8700 but My top end load for H-50 BMG was 100 grains behind either a 168 SMK or a 169.5 wildcat and on hot days ( above 85 ) will show pessure ( developed that load during the cold months ). So far I'm up to 102 grains of WC872 with the same bullets and have reached the <u> <font color="red"> </font> same velocity </u> <font color="blue"> </font> as H-50 BMG but have not gotten any pressure signs what so ever! I intend upon going up with the powder once again to wherever I get the best results or pressure signs. This tells me it burns slower than H-870, AA8700, and H-50 BMG powder since I have exceeded the previous load data for each powder by 2 full grains already.
#3 Kirby and jwp 475 also found the WC872 to be a slower burning powder in their tests by exceeding H-870 load data by a good margin along with H-50 BMG data as well.
#4 As far as barrel heat I have not used any hi tech device to measure it but when you can feel a difference by grabbing the barrel after 3 shots of the same bullets only different powder then there must be a difference. True I have not reached max level of WC872 yet and when I do there may be no noticable barrel heat difference at all and when I get there I will say I found no noticable difference in barrel heat at max loads for each powder. Right now it's a night and day difference between the 2 after 3 shots The BMG I assure you that you will turn it loose shortly after grabbing it and the WC872 you can hold with no pain or teeth gritting for as long as you want.
Like I said I don't want to argue mathmatics because I hated frieking equations and formula's in school and I don't like them any better now.
I'm only stating facts that I have so far and when I get more data collected on this subject I will share it over on a thread of mine in equipment reviews titled Wildcat bullets consistency and accuracy.
I'm through hijacking Kirby's wonderful thread about his new Allen Mag.
Sorry for the Hijack Kirby, Len, Dave, Ian ! /ubbthreads/images/graemlins/frown.gif
Buffalobob
Well-Known Member
Add into the mix the fact that the Sierra 175 Mk has a lenght that is about 0.05 greater than the 160AB and has a BC of 0.6 and you find that there are some really good heavy bullets for the 7mm.
7Rumloader
Well-Known Member
Re: wc872 burn rate
Dave I understand b1g b0re's point on that aspect.
He is correct so far in saying not as much pressure I will not argue or contest that point at all because I'm not to max pressure with WC872 like I am with H-50 BMG. There for what I was saying is so far my velocities are the same but pressure is not and barrel temp is not as high either.
I will finish my tests one day when Kirby and Chris and Shawn let me take a day off /ubbthreads/images/graemlins/grin.gif but until then I will state what i know so far.
Dave I understand b1g b0re's point on that aspect.
He is correct so far in saying not as much pressure I will not argue or contest that point at all because I'm not to max pressure with WC872 like I am with H-50 BMG. There for what I was saying is so far my velocities are the same but pressure is not and barrel temp is not as high either.
I will finish my tests one day when Kirby and Chris and Shawn let me take a day off /ubbthreads/images/graemlins/grin.gif but until then I will state what i know so far.
7Rumloader
Well-Known Member
ss7mm you are very correct about the 169.5 I have found them to be very accurate in my factory RUM as well.
I know the feeling about spending bookoo dollar on guns because right now I have 3 on my list from Kirby and at least 1 each from Shawn and Chris /ubbthreads/images/graemlins/blush.gif( not counting a rebarrel here soon ) and with only one in the works and me pulling double shifts so I can get at least 3 new rigs in before my birthday next March. /ubbthreads/images/graemlins/grin.gif
I know the feeling about spending bookoo dollar on guns because right now I have 3 on my list from Kirby and at least 1 each from Shawn and Chris /ubbthreads/images/graemlins/blush.gif( not counting a rebarrel here soon ) and with only one in the works and me pulling double shifts so I can get at least 3 new rigs in before my birthday next March. /ubbthreads/images/graemlins/grin.gif
ricka0
Well-Known Member
Re: wc872 burn rate
[ QUOTE ]
<font color="purple">Not an expert by any means,but your formula is not taking into account the powder burn rates and the area in which they're burned. </font>
[/ QUOTE ]
Actually it does take into account burn rate. That's what I'm talking about the integral of the P function (the area under the curve of the graph). The area where they are burned would only matter if you had dirac type impulses, which you don't. The pressure is relatively low compared to high explosives.
[ QUOTE ]
<font color="brown"> Complex high pressure non-equilibrium systems often deviate substantially from ideal gas law behavior.</font>
[/ QUOTE ]
Powder burning is neither. You'd be right for high explosives.
[ QUOTE ]
<font color="brown"> The book gun propulsion technology (progress in astronautics and aeronautics) discusses propellant additives used to reduce burn temperature. </font>
[/ QUOTE ]
And reducing temp reduces pressure - unless magic comes into play.
[ QUOTE ]
<font color="brown"> There are also recent studies of additives for prolonging barrel life in artillery. </font>
[/ QUOTE ]
No question there are things you can do to prolong barrel life - but that has nothing to do with the fact burning powder is a good aprox of PV=nRT. Can you site any literature refuting such? Do you have an explanation on how a lower temp can produce equal pressure? (One would be the formation of new gas molecules - increasing the n - but chemists I've talked to say powders don't differ in this regard.)
[ QUOTE ]
<font color="purple">Not an expert by any means,but your formula is not taking into account the powder burn rates and the area in which they're burned. </font>
[/ QUOTE ]
Actually it does take into account burn rate. That's what I'm talking about the integral of the P function (the area under the curve of the graph). The area where they are burned would only matter if you had dirac type impulses, which you don't. The pressure is relatively low compared to high explosives.
[ QUOTE ]
<font color="brown"> Complex high pressure non-equilibrium systems often deviate substantially from ideal gas law behavior.</font>
[/ QUOTE ]
Powder burning is neither. You'd be right for high explosives.
[ QUOTE ]
<font color="brown"> The book gun propulsion technology (progress in astronautics and aeronautics) discusses propellant additives used to reduce burn temperature. </font>
[/ QUOTE ]
And reducing temp reduces pressure - unless magic comes into play.
[ QUOTE ]
<font color="brown"> There are also recent studies of additives for prolonging barrel life in artillery. </font>
[/ QUOTE ]
No question there are things you can do to prolong barrel life - but that has nothing to do with the fact burning powder is a good aprox of PV=nRT. Can you site any literature refuting such? Do you have an explanation on how a lower temp can produce equal pressure? (One would be the formation of new gas molecules - increasing the n - but chemists I've talked to say powders don't differ in this regard.)
ricka0
Well-Known Member
Re: wc872 burn rate
[ QUOTE ]
I'm not to max pressure with WC872 like I am with H-50 BMG.
[/ QUOTE ]
wc872 is the better powder for you. I'm ordering some myself (not for my 50 BMG's tho). Amazing it works so good and is so cheap - breaking the old cliche <font color="green"> You get what you pay for </font>
If it works for Kirby I'm betting it will work in my Kirby guns
Now if I end up having Kirby build me a 7mm with a 48" barrel, I might look for an even slower burning powder.
[ QUOTE ]
I'm not to max pressure with WC872 like I am with H-50 BMG.
[/ QUOTE ]
wc872 is the better powder for you. I'm ordering some myself (not for my 50 BMG's tho). Amazing it works so good and is so cheap - breaking the old cliche <font color="green"> You get what you pay for </font>
If it works for Kirby I'm betting it will work in my Kirby guns
Now if I end up having Kirby build me a 7mm with a 48" barrel, I might look for an even slower burning powder.
7Rumloader
Well-Known Member
Re: wc872 burn rate
the only trouble I see with the Wc872 powder is like Kirby already stated. You have to run <u>near</u> max pressure or you will have a coal factory in your barrel and also it's not temp resistant like the Hodgdon extreme series that the H-50 BMG is a member of.
I like it so far and as you said it's hard to beat at 40 bucks for 8 pounds!
I did however find it for less on another site later but not much.
[ QUOTE ]
Now if I end up having Kirby build me a 7mm with a 48" barrel, I might look for an even slower burning powder.
[/ QUOTE ] Now thats a long tube! /ubbthreads/images/graemlins/shocked.gif
the only trouble I see with the Wc872 powder is like Kirby already stated. You have to run <u>near</u> max pressure or you will have a coal factory in your barrel and also it's not temp resistant like the Hodgdon extreme series that the H-50 BMG is a member of.
I like it so far and as you said it's hard to beat at 40 bucks for 8 pounds!
I did however find it for less on another site later but not much.
[ QUOTE ]
Now if I end up having Kirby build me a 7mm with a 48" barrel, I might look for an even slower burning powder.
[/ QUOTE ] Now thats a long tube! /ubbthreads/images/graemlins/shocked.gif
Ballistic64
Well-Known Member
Re: wc872 burn rate
OK,but is it not possible to have two powders with different burn rates in which one is completely burned with the bullet half way down the barrel and the other with the bullet three quarters of the way down the barrel produce the same pressure but with the latter at a lower temp because of the larger area its burned in?
Im not disputing you bigbore,just trying to understand because I dont really understand your formula. /ubbthreads/images/graemlins/confused.gif
OK,but is it not possible to have two powders with different burn rates in which one is completely burned with the bullet half way down the barrel and the other with the bullet three quarters of the way down the barrel produce the same pressure but with the latter at a lower temp because of the larger area its burned in?
Im not disputing you bigbore,just trying to understand because I dont really understand your formula. /ubbthreads/images/graemlins/confused.gif
Jon A
Well-Known Member
Re: wc872 burn rate
The ideal gas law has very little to do with this subject.
Nowhere in the law does it account for a solid undergoing a chemical reaction and changing phases. That reaction (burning) will take place at different temperatures for different elements regardless of how much gas is produced. This is where much of the heat of firing comes from--not simply a gas being compressed.
Even if you try and apply it after combustion is complete (and at this point you are already well beyond peak pressure) different powders can have a different number of moles of gas which is a variable you don't know unless you know the exact chemical composition of each powder.
So yes, it is completely possible for two different loads for a rifle with two different powders to reach the same peak chamber pressure at much different temperatures.
Stick your finger in a hydraulic press and you'll see it doesn't take temperature to create pressure. The ideal gas law doesn't apply to that either. No magic required.
The ideal gas law has very little to do with this subject.
Nowhere in the law does it account for a solid undergoing a chemical reaction and changing phases. That reaction (burning) will take place at different temperatures for different elements regardless of how much gas is produced. This is where much of the heat of firing comes from--not simply a gas being compressed.
Even if you try and apply it after combustion is complete (and at this point you are already well beyond peak pressure) different powders can have a different number of moles of gas which is a variable you don't know unless you know the exact chemical composition of each powder.
So yes, it is completely possible for two different loads for a rifle with two different powders to reach the same peak chamber pressure at much different temperatures.
Stick your finger in a hydraulic press and you'll see it doesn't take temperature to create pressure. The ideal gas law doesn't apply to that either. No magic required.
Richard338
Well-Known Member
- Joined
- Aug 22, 2003
- Messages
- 126
Re: wc872 burn rate
You are correct Jon A. I work in science and occasionally search the literature for references and patents in these areas. There are some fairly sophisticated internal ballistics codes that have come out. They do not rely on the ideal gas law. Even low pressure Helium doesn't strictly obey the ideal gas law. Accurate modelling of any REAL gas is much more complicated. You should load your cartridge with Magnesium-Teflon-Viton (MTV) and then see if you believe in hotter powders!
You are correct Jon A. I work in science and occasionally search the literature for references and patents in these areas. There are some fairly sophisticated internal ballistics codes that have come out. They do not rely on the ideal gas law. Even low pressure Helium doesn't strictly obey the ideal gas law. Accurate modelling of any REAL gas is much more complicated. You should load your cartridge with Magnesium-Teflon-Viton (MTV) and then see if you believe in hotter powders!
ricka0
Well-Known Member
Re: wc872 burn rate
[ QUOTE ]
<font color="purple"> The ideal gas law has very little to do with this subject. Nowhere in the law does it account for a solid undergoing a chemical reaction and changing phases. That reaction (burning) will take place at different temperatures for different elements regardless of how much gas is produced. This is where much of the heat of firing comes from--not simply a gas being compressed.
</font>
[/ QUOTE ]
I'm afraid you have misunderstood the ideal gas law (IGL) and what I have written. According to the chemists I've talked to, (and previously posted) there is <font color=" green"> virtually no phase changes </font> going on or creation of new gas molecules. (If you can cite a credible reference stating otherwise I'd love to see it.) You merely have a heat pump – and a very slow burning one at that – much like the fuel burning in your cylinder (engine). In the case of internal combustion engines, you do have some deviation from a pure heat pump in that the <font color="red"> n </font> in <font color="red"> PV=nRT </font> increases minimally (i.e., new gas molecules are created) This situation does not occur with burning powder. The creation of more <font color="red"> n </font> still fits into the IGL but cannot be reduced to a simple heat pump (altho the <font color="red"> n </font> increase in an internal combustion engine is minimal so the heat pump simplification is still a good approximation.
My guess is that the reason powder that is not sealed changes density over time is because powder is hygroscopic (absorbs water). In this case there would be a phase change, but water going from liquid to gas absorbs a jynormous amount of energy (thus dramatically cools the reactants) and the increase in <font color="red"> n </font> is far offset by the Jynormous decrease in <font color="red"> T </font>
[ QUOTE ]
<font color="purple">
Even if you try and apply it after combustion is complete (and at this point you are already well beyond peak pressure) different powders can have a different number of moles of gas which is a variable you don't know unless you know the exact chemical composition of each powder.
</font>
[/ QUOTE ]
Incorrect. As I've previous stated numerous times, there is no creation of new gas molecules. You simply have a simple heat pump. Also, you would not quantify via moles without doing the same to all compounds, you would use ratios. Why would you want to apply the IGA after combustion is complete? That's why you integrate.
[ QUOTE ]
<font color="purple">
Stick your finger in a hydraulic press and you'll see it doesn't take temperature to create pressure. The ideal gas law doesn't apply to that either. No magic required.
</font>
[/ QUOTE ]
Obviously there are other ways to create pressure than heat. A hydraulic press is not a heat pump. Hydraulic pressure is produced by hydraulic leverage which supplies the Force or Pressure. Yes, the IGL doesn't apply; hydraulics are fluids – not gasses – and are not heat pumps. A crow bar or hammer produce pressure on a nail head without using heat.
There are many examples of hot gases not approximated by the IGA (ablation in inertial confinement fusion, detonation (supersonic compression, not heat expansion) – but the (relatively) low pressure and burn rate of powders is well approximated by the IGL.
[ QUOTE ]
<font color="purple"> The ideal gas law has very little to do with this subject. Nowhere in the law does it account for a solid undergoing a chemical reaction and changing phases. That reaction (burning) will take place at different temperatures for different elements regardless of how much gas is produced. This is where much of the heat of firing comes from--not simply a gas being compressed.
</font>
[/ QUOTE ]
I'm afraid you have misunderstood the ideal gas law (IGL) and what I have written. According to the chemists I've talked to, (and previously posted) there is <font color=" green"> virtually no phase changes </font> going on or creation of new gas molecules. (If you can cite a credible reference stating otherwise I'd love to see it.) You merely have a heat pump – and a very slow burning one at that – much like the fuel burning in your cylinder (engine). In the case of internal combustion engines, you do have some deviation from a pure heat pump in that the <font color="red"> n </font> in <font color="red"> PV=nRT </font> increases minimally (i.e., new gas molecules are created) This situation does not occur with burning powder. The creation of more <font color="red"> n </font> still fits into the IGL but cannot be reduced to a simple heat pump (altho the <font color="red"> n </font> increase in an internal combustion engine is minimal so the heat pump simplification is still a good approximation.
My guess is that the reason powder that is not sealed changes density over time is because powder is hygroscopic (absorbs water). In this case there would be a phase change, but water going from liquid to gas absorbs a jynormous amount of energy (thus dramatically cools the reactants) and the increase in <font color="red"> n </font> is far offset by the Jynormous decrease in <font color="red"> T </font>
[ QUOTE ]
<font color="purple">
Even if you try and apply it after combustion is complete (and at this point you are already well beyond peak pressure) different powders can have a different number of moles of gas which is a variable you don't know unless you know the exact chemical composition of each powder.
</font>
[/ QUOTE ]
Incorrect. As I've previous stated numerous times, there is no creation of new gas molecules. You simply have a simple heat pump. Also, you would not quantify via moles without doing the same to all compounds, you would use ratios. Why would you want to apply the IGA after combustion is complete? That's why you integrate.
[ QUOTE ]
<font color="purple">
Stick your finger in a hydraulic press and you'll see it doesn't take temperature to create pressure. The ideal gas law doesn't apply to that either. No magic required.
</font>
[/ QUOTE ]
Obviously there are other ways to create pressure than heat. A hydraulic press is not a heat pump. Hydraulic pressure is produced by hydraulic leverage which supplies the Force or Pressure. Yes, the IGL doesn't apply; hydraulics are fluids – not gasses – and are not heat pumps. A crow bar or hammer produce pressure on a nail head without using heat.
There are many examples of hot gases not approximated by the IGA (ablation in inertial confinement fusion, detonation (supersonic compression, not heat expansion) – but the (relatively) low pressure and burn rate of powders is well approximated by the IGL.
ricka0
Well-Known Member
Re: wc872 burn rate
[ QUOTE ]
OK,but is it not possible to have two powders with different burn rates in which one is completely burned with the bullet half way down the barrel and the other with the bullet three quarters of the way down the barrel produce the same pressure but with the latter at a lower temp because of the larger area its burned in?
Im not disputing you bigbore,just trying to understand because I dont really understand your formula. /ubbthreads/images/graemlins/confused.gif
[/ QUOTE ]
You are correct in your example. My explanation accounts for this by integrating the P function over the length of the barrel- which amounts to finding the area under the curve.
I apologise for skipping over this detail and assuming everyone is familiar with calculus - that's what happens when you teach calc too often to undergrads.
Your example is also not what you want in a powder. Ideally you want to get a powder that completes burning just as the bullet exits.
Take another look at the graph I posted in my first response. The pressure curve is not flat - so you need integration to compute the work of the powder.
The holy grail of powder would be a flat curve at peak pressure all the way down the barrel (with a very consistent pressure curve so you have a low ES and Std Dev) - the same as the holy grail in an internal combustion engine is a flat torque curve. (dynamic cams come close to doing this)
I've thought a lot on how I could create a two chamber powder plug so after you reach peak pressure and pressure starts to drop - you would melt thru a barrier to the 2nd powder chamber - the 2nd powder chamber would have a much higher burn rate. All this to flatten the pressure curve and thus produce maximum velocity at safe pressure.
[ QUOTE ]
OK,but is it not possible to have two powders with different burn rates in which one is completely burned with the bullet half way down the barrel and the other with the bullet three quarters of the way down the barrel produce the same pressure but with the latter at a lower temp because of the larger area its burned in?
Im not disputing you bigbore,just trying to understand because I dont really understand your formula. /ubbthreads/images/graemlins/confused.gif
[/ QUOTE ]
You are correct in your example. My explanation accounts for this by integrating the P function over the length of the barrel- which amounts to finding the area under the curve.
I apologise for skipping over this detail and assuming everyone is familiar with calculus - that's what happens when you teach calc too often to undergrads.
Your example is also not what you want in a powder. Ideally you want to get a powder that completes burning just as the bullet exits.
Take another look at the graph I posted in my first response. The pressure curve is not flat - so you need integration to compute the work of the powder.
The holy grail of powder would be a flat curve at peak pressure all the way down the barrel (with a very consistent pressure curve so you have a low ES and Std Dev) - the same as the holy grail in an internal combustion engine is a flat torque curve. (dynamic cams come close to doing this)
I've thought a lot on how I could create a two chamber powder plug so after you reach peak pressure and pressure starts to drop - you would melt thru a barrier to the 2nd powder chamber - the 2nd powder chamber would have a much higher burn rate. All this to flatten the pressure curve and thus produce maximum velocity at safe pressure.
