Burn rates and calibers...

[LRS_Ranger]

While trying to find a good powder for my 405 gr 45-70 loads, I noticed the product description on IMR4198:

"This fast burning rifle powder gives outstanding performance in cartridges like the 222 Remington, 221 Fireball, 45-70 and 450 Marlin. Varmint shooters with small bore cartridges love it."

This got me wondering, how does a powder work well for 223 and 45-70? One is fast and light, the other hucks giant chunks of lead slow. If not for something like 45-70, when would you use a slow powder? Thanks a bunch and pardon my ignorance.... And by the way, anyone have a good load for that powder and 405 Gr laser-cast?

 

[Muttt]

I'm pretty sure the rule of thumb is slow burn for large fast magnums and fast burn for smaller rounds like pistol and medium is for your lighter rifle rounds.

I'd be using a slower powder for my 7mm Rem Magnum. I use a medium powder for my .223 and Grendel.

 

[Blackrock]

The 45-70 is a large bore open mouth case and works well with faster burning powders.

 

[LRS_Ranger]

Thanks for the answers.. but maybe I will rephrase my question.. I'm more interested in WHY.. as in the science of powder choice. I have a feeling that in this case it has to do with the volume of the barrel being large compared to the volume of the case. But then that theory wouldn't hold true for the 223. Is there a good book anyone can direct me to? Kinda like "Understanding Firearm Ballistics" but for reloading. Thanks all..

 

[JimKirk]

Your best bet would be to research "Internal Ballistics". Reading a book or a chapter out of some of the better books on the subject would do more to enlighten than what could be spelled out in a simple post. Look on the NRA web site at the book sections for the subject and of course the net has lots of info too. Just make sure it is from a reliable source.

Jimmy K

Check this link out for some reading sources:

http://www.jbmballistics.com/ballistics/bibliography/bibliography.shtml

http://wetlands.simplyaquatics.com/d/16697-1/intballi.pdf

 

[NCsmitty]

Powder burn speed requirements are basically the ratio of bore size to case volume.

I have a feeling that in this case it has to do with the volume of the barrel being large compared to the volume of the case.

You pretty much figured it out, LRS_Ranger. It works out even when you're talking shotshells. 12Ga shells require faster burning powder when compared to 410 shotshells.



NCsmitty

 

[Zak Smith]

Think about bore area vs. bullet mass vs. powder volume. Your answer lies there.

 

[LRS_Ranger]

Thanks all... good stuff..