How are burn rates controlled?


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gamestalker
April 7, 2013, 09:08 AM
I know this question has probably been asked more than once, but I'll ask again anyway.
What is the process in manufacturing powders such as Green Dot, Blue Dot, and Red dot that produces the varied burn rates? And is the process similar to, or the same, for the other type powders. I know that I've had it explained to me more than once, but I'm getting old and forgetful. It's no big deal, just curious.

GS

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243winxb
April 7, 2013, 09:49 AM
Deterrents coat the exterior of the propellant granules to reduce the initial burning rate on the surface as well as to reduce initial flame temperature and ignitability. The coating also broadens the pressure peak and increases efficiency. Deterrents may be a penetrating type such as Herkoteā, dibutyl phthalate, dinitrotoluene, ethyl centralite, methyl centralite, or dioctyl phthalate; or an inhibitor type such as Vinsolā resin.
http://firearmsid.com/Feature%20Articles/McCord_gunpowder/index.htm I would guess different amount of nitroglycerine change the burning rates. Some MSDS just list a range of 4.0 – 40% for some Alliant "Dot" powder types. http://www.hodgdon.com/msds.html Alliant Powders - http://www.alliantpowder.com/resources/msds.aspx

Waldog
April 7, 2013, 09:50 AM
One of the primary ways to control burn rate is the SIZE of the podwer grains. For example IMR 4831 powder particles are about 10 times the size of particles of Bullseye powder. Just as in a camp fire; twigs burn FASTER than logs.

They also use chemical coatings on the powder and, of course, powder formulation comes into to play as well. Hope that answers helps.:D

kingmt
April 7, 2013, 10:03 AM
One more thing to are in is shape. Ball powder(most common) has the second must surface area & donuts the first.

Walkalong
April 7, 2013, 10:06 AM
Size, shape, deterrents, coatings ....

243winxb
April 7, 2013, 10:33 AM
Links here- http://www.thehighroad.org/showpost.php?p=8610130&postcount=6

gamestalker
April 7, 2013, 10:43 AM
Considering that some very expensive precision equipment is utilized in the process of research and development, what allowable rate and peak pressure variation is afforded? More specifically, if a particular powder produces 30,000 psi with a 20.0 grain charge, in a particular test mechanism, how much wiggle room is likely to be considered acceptable with regard to both the rate, and peak pressures? I'm guessing that the level of acceptance is low balled to reduce the number of mishaps, but even so, I wonder what percentage is considered as being in line with published projections or estimates.

Sorry for the manner in which I posed this question, but I have always had a deep attraction to physics, and science as it applies here.

GS

Magnum Shooter
April 7, 2013, 10:54 AM
As I understand it 3% is the allowable variation in the manufacturing of powder.

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