7mm Allen Mag test rifle finished.....

[royinidaho]

Re: wc872 burn rate

[/ QUOTE ]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 ]

Been thinking the same thing. All you need is an auxillary chamber say on the bottom of the bbl, a flash hole and a check valve.

As the bullet passes the flash hole the powder in the aux chamber is ignited and the check valve closes off the rear portion of the barrel. Lota details to work out but who knows, stranger things have been accomplished.

Hope the above is taken for the humor thatis intended. /ubbthreads/images/graemlins/grin.gif

Keep the discussion going, I really do appreciate the great cross section of talent/education etc. that is on this board.

The whole discussion will go away when projectiles are accelerated via electricity. /ubbthreads/images/graemlins/frown.gif

 

[ricka0]

Re: wc872 burn rate

[ QUOTE ]
<font color="purple"> 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!</font>

[/ QUOTE ]

Great. Provide a citation or explanation for what creates pressure in burning powder besides heat. I've already shown the other alternative n is insignificant.

You are correct in that gases deviate from the IGL - but it is a good approximation and as the chemists have stated - [*]powders are primarily differentiated by burn rate - not reactants. [*]Different powders deviate from the IGL in a very consistent fashion
For all the naysayers of the simple heat pump approximation - please provide an explanation rather than a summary dismissal.

Even some reproducible data with a thermocouple and chrono (controlling for ambient temp.) would be helpful. But simply saying I shot my gun with H-50BMG powder a few weeks ago then wc872 yesterday and the barrel was hotter with H-50BMG shows nothing. How much hotter? What was the shot rate? Ambient temp? Unless you control and measure these factors you only have the impetus to do so, but cannot come to any conclusion.

There are other factors which can explain throat erosion. How abrasive are the powders? Some powders are far more abrasive than others. This is especially important before the bullet forms a gas seal.

This does give me a good idea. Perhaps I can video my 50 BMGs at night (which have a jynormous flame) and see if I can figure out how much unburnt powder remains when the bullet exits.

The reason I'm so familar with bullet acceleration being so well approximated by PV=nRT is my extensive discussions with some chemists in my quest for a multi-stage powder that can flatten the pressure curve. I'm not the first to think of this idea.

 

[ricka0]

Re: wc872 burn rate

<font color="purple"> [ QUOTE ]
7mmRUM: the only trouble I see with the Wc872 powder is like Kirby already stated. You have to run near max pressure or you will have a coal factory in your barrel

[/ QUOTE ] </font>
If you clean your barrel often, is this a problem?

 

[Richard338]

Re: wc872 burn rate

BigBore,
You say that I am summarily dismissing your points. I am not, but I think that you are dismissing mine. I can find some references at work tomorrow. For that matter who are the chemists who told you that burning powder produces no gaseous products? I'm a chemist myself. I don't know everything about propellant chemistry, but I know that powders have a wide range of formulations. They can be single-base, double-base, or triple base. They include different amounts of plasticizers, burn rate modifiers and possibly coolants. So I would say that the chemistry of different powders burning could be quite different. It doesn't take the conditions of a detonating high explosive to deviate from the ideal gas law. All real gasses deviate.

 

[Richard338]

Re: wc872 burn rate

BigBore,
I'm trying to think about your points. Maybe you can clarify what (in your mind) is happening during combustion?
If only heat is being produced, then how? Don't you think that chemical change and creation of reaction products is producing the heat?
I found one reference for you already:
MODEL FOR COMBUSTION OF TRIPLE-BASE PROPELLANT WITH
DETAILED CHEMISTRY

http://www.asc2004.com/Manuscripts/sessionD/DP-11.pdf

They discuss a variety of gaseous products formed by propellant combustion (and some reactions among those products).

 

[ricka0]

Re: wc872 burn rate

[ QUOTE ]
<font color="purple"> 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 </font>

[/ QUOTE ]
Double ditto on the Hijack apologies.
You guys are doing the important work - what powder (and load) produces the best results. I was only listing published burn rates - I'm not sure they are accurate. I plan on getting an 7mm Allen uber mag some day. I'm Kirby's biggest fan.

Burn rate is dynamic and dependent on many factors, temp and pressure being significant. Perhaps if you compared the H-50BMG and WC872 pressure curves you would see the H-50BMG spiking to max pressure then dropping off quickly (less area under the curve) - so less terminal velocity from the H-50BMG. Because H-50BMG (guessing here) drops off so quickly, when the bullet exits, there is still plenty of powder left burning to heat your barrel. If my conjecture is true, your barrel will last longer with WC872 while producing higher velocities.

Without temp, vel and pressure curve data, it's all conjecture. What is fact and not conjecture is that WC872 produces superior results - and that's really what we are all after.

I've ordered several batches of WC872 so I can get similar good results in some of my rifles.

And for the zillionth time: <ul type="square"> [*]I agree, no gas exactly follows the IGL - but for simple heat pumps (like guns) it is an excellent model [*]If the well understood and accepted heat pump mechanism is not the primary accelerator of bullets, provide credible evidence/explanation of an alternative mechanism such that two appropriate powders can produce the same terminal velocity with different heat flux. By appropriate I mean not using a powder that burns so slow much of the powder burning occurs after bullet exit and simply contributes to kick and heating the barrel. [/list]

2nd Summary: <ul type="square"> [*]Kirby makes the hottest/flattest shooting wildcats [*]Kirby's uber mags like WC872 [*]The only thing that matters is the measured performance (velocity/accuracy) of these guns. (And RUMS, I have 4 RUMS /ubbthreads/images/graemlins/smile.gif ) [/list]

 

[Ballistic64]

I apologize also Kirby,we should have started a new thread but what bigbore was getting into is pretty interesting,sorry. /ubbthreads/images/graemlins/cool.gif

 

[Eaglet]

Fiftydriver,
Please, I'm also joining, receive my apologies. It was rude of all of us. We'll try to behave better in the future!
Say something man!

 

[Fiftydriver]

Holy CRAP!!!!

I guy is away from the shop for a day and a half to a family reunion and when he gets back theres +40 new posts to read!!! /ubbthreads/images/graemlins/shocked.gif

Well, I read all the posts and while I wanted to reply to each one individually, I also want to get some sleep tonigh!!

So I will group my comments together.

First off, all this discussion has alot to do with big cases, heavy bullets, and high performance. I do not see a hijack going on here. Powder selection is probably second only to bullet selection in my mind for the Allen Mags to get top performance.

That said, I agree that 50 BMG is totally suitable for the 7mm Allen Mag with the 175 and 200 gr bullets, I have just not gotten to the point of actual testing yet. It will come though.

As far as Burn temps with ball and stick powders, I have no scientific data to type to back up my comments, what I do have though is test a barrel using Retumbo chambered in 257 STW and then taking that exact same barrel and testing it with AA8700 in my Allen mag and actually being able to feel the difference in barrel temp with my hand. Five shots with the STW and I could not hold the barrel, 8 shots with the AA8700 and while the barrel was very warm, I could hold it comfortable.

You guys know far more then I do about scientific testing, I am just a simple rifle maker that sees things pretty black and white and to me the ball powders keep barrel temps lower.

This may be to some result of less bore friction caused by the powder itself???

Comparing AA8700, H-870, H-50BMG and WC872. The current lot of 8700 I have has a burn rate nearly identical to Retumbo. I deduce this from the fact that in the 270 Allen Mag, they produce nearly identical velocities with the 130 gr Ballistic Tip when using the same powder charge.

The earlier lot of 8700 was nearly identical to the old H-870 which I have found to be at least the same or slower burning then H-50BMG. I say this because in the 50 BMG I get less velocity with the same powder charge under the same bullet using H-870 compared to H-50BMG which again tells me that the ball powder is slower.

Please keep in mind that in cool temps that H-870 may be slightly slower then H-50BMG and in warmer temps it may be slightly quicker burning.

I will tell you that I have never seen a lot of AA8700 or H-870 burn as slow as the lot of WC872 I am using now.

Again, I am a simple guy, from what the data tells me this is how I would rate these powders in burn rate:

AA8700

H-870/H-50BMG very close on average

WC-872

Now the difference between 870/50BMG and 872 is not dramatic but it is there.

Also, thanks for the pics of the 200 gr ULD in comparision to the 160 gr Accubond. My figures that stated the 200 gr ULD was 0.060" longer then the 160 gr Accubond was in reference to the full diameter body of the bullet which was clearly illistrated by ss7mm, thank you!!

I will read through the posts again tomorrow as I am sure I missed some things I wanted to touch on.

Basically, I am happy with the results so far with the 7mm Allen Mag but to be honest until we get the 1-7 30" barrels to test, we are just playing around with this round. Data will continue to come in as soon as I get it tested on the range. I will be testing some 175 gr SMKs next to see what we can do in a 26.5" barrel. Basically the reason for this testing is to get me a start on the 175 gr ULD RBBT bullets as I know they will be a superior bullet option. Not that the Sierra is a good bullet because it is, its not a Wildcat though!!

I will reply more tomorrow, good night and great conversation, no need to apologize to me.

Kirby Allen(50)

 

[Richard338]

BigBore,
OK I found some references. I can't find anyone who treats internal ballistics as a heat pump with no gaseous combustion products. The references I will list below detail a complex mixture of pressure producing reaction products. In fact one is a patent application to use double-base propellants as a gas-generator for fire extinguishers.
It seems well established that combustion of propellants produces large amounts of various gasses.
This was my original intuition that you kept flatly discarding while saying "the chemists say..". I told you that I was a chemist, but you just kept stating that it is a simple heat pump and disregarding anything that anyone said to the contrary. If you still believe it is a simple heat pump then can you:
1) tell me exactly how you think it works. Have you done a back of the envelope calc on the volumes, temps and pressures (using the ideal gas law)?
2) Who are the chemists that told you that?
3) What do you think of the references I list below? I remember now that one ref I already gave you (Gun propulsion tech) covers many details of the combustion process such as grain geometry and chemical composition.

Reaction products of propellants and explosives. Volk, F.; Bathelt, H.; Jakob, R. Fraunhofer Inst., Pfinztal-Berghausen, Fed. Rep. Ger. International Annual Conference of ICT (1988), 19th(Combust. Detonation Phenom.), 13/1-13/25. CODEN: IACIEQ ISSN: 0722-4087. Journal written in German. CAN 112:201692 AN 1990:201692 CAPLUS

Abstract

Mass spectrometry was used to study the combustion products of single-, double-, and triple-base propellants. High contents of NO along with H, N, CO, CO2, H2O, CH4, and N2O were obsd. in the combustion products of single- and double-base propellants, this indicating that the combustion conditions were nonequil. The amt. of NO in the combustion products of triple-base propellants was much lower than the amt. calcd. from the nitrate ester content. Nitramine-contg. propellants yielded a very high HCN content along with NO and other gases. The gas compn. and explosion heat in the low-pressure region were compared with data obtained in a pressure bomb.


Calculation of thermodynamic parameters of combustion products of propellants under constant volume conditions. Suceska, Muhamed. Brodarski Institut - Marine Res. Special Technologies, Zagreb, Croatia. Kemija u Industriji (1998), 47(4), 151-163. CODEN: KJUIAR ISSN: 0022-9830. Journal written in Croatian. CAN 128:310152 AN 1998:316498 CAPLUS

Double-base propellants for gas generating compositions for expelling Halon-replacement fire extinguishers. Neidert, Jamie B.; Black, Robert E. (USA). U.S. Pat. Appl. Publ. (2002), 8 pp. CODEN: USXXCO US 20020007886 A1 20020124 Patent written in English. Application: US 99-370171 19990809. CAN 136:137127 AN 2002:72635 CAPLUS


Reaction products of nitrocellulose and nitramine containing propellants. Volk, F. Fraunhofer Institut Chemische Technologie, Pfinztal, Germany. Proceedings of the International Pyrotechnics Seminar (1996), 22nd 717-724. CODEN: PPYSD7 ISSN: 0270-1898. Journal written in English. CAN 125:146438 AN 1996:508416 CAPLUS


Relation of flame temperatures to propellant combustion products compositions. Davidchuk, E. L.; Mal'tsev, V. M.; Margolin, A. D.; Petrov, Yu. M.; Ryabikov, O. B. Inst. Khim. Fiz., Moscow, USSR. Fizika Goreniya i Vzryva (1977), 13(1), 132-5. CODEN: FGVZA7 ISSN: 0430-6228. Journal written in Russian. CAN 86:192051 AN 1977:192051 CAPLUS


Grune, D.; Aulinger, F.; Zeller, A. Study of the reaction products of double-base and triple-base powder propellants after combustion in the high-pressure bomb followed by rapid expansion: comparison of theoretical and experimental values. Report (1986), (ISL-CO-252/86; Order No. PB88-146972), 26 pp. CAN 109:233662 AN 1988:633662 CAPLUS

 

[Jon A]

Re: wc872 burn rate

[ QUOTE ]
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.)

[/ QUOTE ]
I guess I drink way too much beer when I reload. I simply have no memory of ever filling a case with a compressed gas. Is that sort of like putting air in the tires of your truck? Or filling a propane tank (hey even that one has a phase change too!)?

Sorry, but I don't need to cite "sources" to tell me what I'm dropping in the case is a lot of small chunks of a solid. And what comes out of the barrel is mainly gas. And that there's a burning process in between responsible for the change which creates a large portion of the heat the barrel recieves.

Your whole PV=nRT model would likely work well for a Daisy air rifle.

 

[Richard338]

Re: wc872 burn rate

BigBore,
Some more info for your info.

http://www.fas.org/man/dod-101/navy/docs/fun/part16.htm

Relevant excerpts
17.3.2 Propellants.

Triple-base propellants are double-base propellants with the addition of
nitroguandine to lower the flame temperature...

17.3.3 Burn Rates.

Solid propellants are designed to produce a large volume of gases at a controlled rate.

17.3.5 Interior Ballistics.

When the charge is ignited, gases are evolved from the surface of each grain of propellant,
and the pressure in the chamber rises rapidly. Due to friction and resistance of the rotating band,
the projectile does not move until the pressure behind it reaches several hundred pounds per square inch.
For a time after the projectile starts to move, gases are generated more rapidly than the rate at which
the volume behind the projectile in increased, and the pressure continues to rise...


The above info talks pretty clearly about gas production.

I didn't notice before that you said the holy grail of a pressure curve would be constant (flat until the bullet exits the muzzle).
That is the first thing dealt with in Gun Propulsion Technology in the section about how propellant is designed.
They say that naively considering that the velocity is given by the integral of the pressure curve, and that the gun can withstand only a certain max pressure one might think that a flat pressure curve is desirable. In fact it is not, and they explain why.
If you are really interested in these things you should really read that book.

 

[davewilson]

Re: wc872 burn rate

Jon A, i agree with you.i hate to get technicle,but the only phase change i see is before you pull the trigger,it's very quiet and after,it's very loud!

50, now about that twist rate.will a 9 stabilize those 200's?

 

[Fiftydriver]

Re: wc872 burn rate

Dave,

My personal opinion is NO, the 1-9 will not stabilize the 200 gr ULD. That said, I have shot the 145 gr FBSP Wildcat in my 257 Allen Mag with a standard 1-10 twist with excellent results so I will hold my judgement on this topic for now.

I just got a shippment of these big monsters in today so I will be testing soon in the 1-9 Shilen for nothing else but to see what velocity I can get with the 200 gr pills. If they land full profile, they will have trememdous Knock Down power /ubbthreads/images/graemlins/grin.gif!!!

Just kidding!!

I will let you know soon. The computer models are recommending 1-7 twist barrels and that is what we had Dan Lilja tool up to build for the 7mm Allen Mag, a 1-7 3 groove barrel.

Kirby Allen(50)