Blue Dot vs 2400......

[Salmon-boy]

I've been reloading for all of about 8 months now, so I'm still new to this..

Most burn rate charts I've looked at place Blue Dot and 2400 at about the same speed, yet take the .30 Carbine for instance - 8.8gr max Blue Dot vs 11gr for 2400.

Ok, is there a real difference here? Or maybe the real question is how well should I trust a rate chart for working up loads with available powders?

[GabbyM]

Can't give a scientific explanation due to lack of background.

Simply put the burn rate is just that. How fast powder burns. You also have other factors. Like energy content of the powder. Accurate powder load books give the % of nitroglycerin in their powders. Ranges from 21% to 10%. Then their's bulk density that determines how much weight you can stuff into the cartridge.

The same powder may perform differently in various calibers.

You need to use the load data for your caliber and bullet weight. Even then you'll have variation between different guns. Most powder manufacturers have load data on their web pages anymore. So it's easy to find.

[felix]

You need lots of experience to understand the powder burn rate charts as presently given. The charts DO NOT have a line between significant burn-speed groups. BlueDot and 2400 are in two distinct groups. BlueDot is the slowest powder of the mid-speed pistol group, whereas 2400 is the fastest of the slow-speed pistol group. There used to be a powder exactly in between the two groups. That powder is/was WW630. It was taken off of the market because its speed could not be kept consistent. It's formulation was composed of a mixture of powders from each of the outer groups, and the individual powders became separated in travel and in use. A sophicated user would mix the powder upon receipt and keep the powder hopper filled no more than half full when powder dumping/banging took place. ... felix

[Salmon-boy]

Felix, thanks! Good explanation for my needs!

Without getting into the Thermo- and Fluid- dynamics associated with combustion, I'm kind of getting the idea that a powders' burn rate is determined by pressure in the case (hence different powders for different size cases and barrel lengths) and composition (both chemical and physical), all determining how much gas is produced.

Am I off the mark?

[felix]

Right on! ... felix

[Ricochet]

Burn rate charts merely give an approximate order of burn rates and show nothing about actual burn rates.

There are powders adjacent to each other on the tables with wide gaps in their burn rates, and there are long strings of powders that are nearly identical.

Powders change their burning rates under different conditions and can swap positions in different loads. The burn rate table will tell you that Bullseye, for instance, burns faster than Red Dot. Alliant says on their pages that Red Dot burns at 94.1% of the speed of Bullseye. But Alliant's own loading data shows numerous instances where smaller charges of Red Dot give similar velocities and pressures to larger charges of Bullseye.

[Salmon-boy]

There's a burn chart I saw (bookmarked on another computer) which separated out the powders by class, but I can't find it for the life of me.

I did find a good read though -> http://www.chuckhawks.com/powder_burn_rate.htm

From there, one thing stands out - Burn Rate is only one of several preliminary considerations. Exactly what I was using it for..

It makes sense to me now as to why I couldn't find a good article or book on the art of powder selection! One good read on internal ballistics can be found here -> http://www.frfrogspad.com/intballi.htm

[gon2shoot]

Don't go there!
Comparison charts are not intended for load data transfer. Please stay with documented load data per powder.
Most powder Co.s have a website with data available.