Rossi Rifleman

This is a short video demonstration of the different burn rates of the powder Speer uses
in their Gold Dot 223 64 grain and 75 grain ammo. Burn starts about the 1 minute mark.

[BBvideo 560,340][/BBvideo]

I can understand the logic of a burn rate that allows all the powder to burn
before the bullet leaves the barrel.

But what is the down side of a faster than necessary burn rate
that completes its burn when the bullet is halfway through the barrel?

could it be that the pressure curve, based on bullet weight, is factored in to give the burn rate to bullet weight the proper fix? The barrel pressure created by light weight bullets and heavier weight bullets will be a major factor.

Maybe I'm just babbling, but it makes sense to me.


jd

There are a lot of factors involved in contained combustion that aren't evident in uncontained burning.
As for the pressure curve you have an absolute maximum pressure limit set to avoid failure of the system including containment of the combustion gases by the brass case/primer and avoid breakage of the firearms components. THEN in the case of a gas operated firearm a-la AR-15 you have a target pressure at the gas port needed to operate the mechanism again without breaking anything.

The powder type that works best for a given caliber generally does change with changes in bullet weight and also bullet composition. The force required to force a jacketed bullet down a barrel is different from the force required for a solid copper one and still different from a lead projectile. A soft lead bullet base won't withstand the same force that a gas checked hard cast or jacketed bullet base will.

Different types of powders can have different granule size, shapes, have holes through them such that the surface area burning remains nearly constant during the burn or have layers 'doped' with burn retardants so that the larger area that starts burning does so more slowly than the smaller surface area once the burn is half done.

A faster burn rate powder may risk exceeding the maximum pressure limits to the point that something breaks OR may limit the amount of powder so that you get much less force on the bullet (think area under the burn curve) because the lesser amount of powder in the case so that you avoid spiking past the pressure limit burns out faster.

The combustion INSIDE the barrel/case is going to be at a different rate than it is uncontained (in the sink) increases in pressure tend to make chemical reactions faster and more complete.

In truth while the video is somewhat interesting I'm not certain it means much since we don't know the powder type in question, amount of powder in the case OR amount of powder in each line in the sink OR whether or not each line of powder covers the same length OR area etc.. Basically you could vary those factors minutely and potentially get enough different effects in the burn that might change what you think you see.

I couldn't tell the difference.

GasGuzzler wrote:I couldn't tell the difference.

bing bing bing!

More in terms of color/intensity of the flame than flame front speed IMO.

I'm not sure what this guy is trying to suggest with his demonstration, but I think it is impossible to measure other than with pressure trace equipment. Smokeless needs to be contained and confined/compressed otherwise it is just really expensive fertilizer.

exactly

Tough crowd!

A table of relative burn rates. I presume it goes slow to fast, but it doesn't say. It is clear that the relative differences could be insignificant or large. Test conditions are not specified, so take with a grain of salt.

HarryAlonzo wrote:A table of relative burn rates. I presume it goes slow to fast, but it doesn't say. It is clear that the relative differences could be insignificant or large. Test conditions are not specified, so take with a grain of salt.

fast to slow