Powder burn rate

[Guest]

The 6th edition of Nosler Manual on page 36 bottom of the right column says "feet per second divided by grains of powder = burn rate". Then it says on page 37 top of the left column, "In the load data that follows the fastest burning powder is listed first, the slowest last".

If you start at the top of the page dividing the velocity by grains of powder the listing goes from slowest to fastest burning posders as you go down the page. This is opposite from waht they stated as I copied in the above paragraph. Am I looking at this wrong.

Example is page 335. Top of page shows 3061 fps/66 = 46.4 burn rate.
Bottom os page shows 3340 fps/67.5 = 49.5 burn rate.
The fastest is at the bottom of the page or last. ?? ??? ?? Am I losing my marbles? Explanation please??

 

[Richracer1]

You, missed a very important part of the paragraph on page 37. That bit of info is, "It should be noted, however, that a given powder does not always produce a faster burning rate than another powder in every cartridge."

If your so worried about powder burn rates, check out the powder manufacturer websites for their published burn rate charts. You will find that they are not the same, but very close to each other.

 

[DrMike]

Powder burn rates are always relative, varying considerably batch to batch. Your question notes a deviation in the published data, but it has no practical effect on the loads you produce. In general, the data published is derived as stated. However, relative quickness (commonly referred to as powder burn rate) is affected by a variety of conditions, including the shape of the powder granules, composition of the powder, coatings employed, moisture content of the powder, relative humidity when tested, etc. Also, the same powder may burn at a different rate in different cartridges due to pressure differentials imposed by case volume, etc. Nosler ballisticians stated their method of establishing how to present the data generated. Essentially, that is all that they have stated without being constrained to adhere tenaciously to their own methodology as it is of little moment.

 

[Guest]

Thanks Dr.Mike. I was just a bit baffled by the inconsistencies in there data .... ie. the loading data listing not following the introductory explanation they gave. I am not overly concerned with the burn rate but I am interested in studying all factors that affect the performance of bullets. Burn rate is one of those factors. Thanks for your input.

richrace1, Reloading manuals are suppose to be the bible of reloading. The only way I can learn from them is try to figure out inconsistencies when I find them. I am not overly concerned with burn rates but this seemed to me to be an inconsistency and I was interested in knowing why. Your suggesting about checking manufacturers burn rate date sounds like a good one. Thanks for your input.

 

[JD338]

To me, burn rates is just a basic for fast/slow burning powders. Some cartridges perform better with one over the other. What I want is a full case of powder for consistency.

JD338

 

[Richracer1]

richrace1, Reloading manuals are suppose to be the bible of reloading.

I wouldn't use the word "bible" for reloading manuals. IMO, loading manuals are guides and nothing more. I always look at my Nosler #6 to start with then compare that to Hodgdon's information (if using Hodgdon products) and once in a while, they are the same, but not very often.

Good luck on your loading and be careful.

 

[DrMike]

You sometimes hear hand loaders speak of determining loads by referring to a burn rate chart. I doubt that any ballisticians do that. There is a general understanding of the relative quickness, but a wise hand loader will not try to substitute the chart for data that has been generated and carefully analysed.

What I want is a full case of powder for consistency.

+1 For accurate ammunition, this is the proper starting point.

Loading manuals are guides

. +1 Can't be said often enough!

 

[Ol` Joe]

If you check the powder companies "burn charts" you`ll find they vary for each other too in some cases. Powders will swap places at times and I`ve even seen them move a place or two in direction. I like to think of the burn charts as a place to find an alterative powder for one I can`t find or that isn`t quite working out in my cartridge. The charts will tell me for example, if I don`t like compressing H4350 I can use W760 which is "similar" in burn or maybe R19 and expect acceptable results from one of them.
Their burns are close on the charts but, they definatly are not the same. They offer a idea of what else is available that should fit a similar application.

 

[Antelope_Sniper]

+1 on all the above.

I keep a burn rate chart posted on my powder cabinet. Interspersed with the canister powders on the list, are the best estimates various commercial and surpluss powders I use. The goal is just like JD described: Find the slowest possible powder, that completely fills the case, but not so slow that you begin loosing velocity.

Here are a couple of rules when choosing powders.
The larger the case, the sharper the bottleneck, the longer the barrel, the slower the powder you are looking for.