Question about powder

[grumpy1]

I know little about powder. When read the load data I have noticed that as the bullet weight goes up the grains of powder go down. I was wondering what am I missing because using logic knowing nothing about powder that seems to opposite what I as a know nothing person would think.

[Winger Ed.]

It has to do with keeping within a safe level of pressure required/generated to get a heavier and heavier object moving.

The heavier something is, there is more resistance and it is harder to get moving down the barrel.
As the pressure curve comes on,,, the bullet has to be able to 'get out of it's way' within chamber pressure limitations.

If You used enough powder to get a 500 grain bullet out a barrel at say,,,,,, 3000 fps
compared to a 100 grain exiting at 3000, all the extra pressure needed would probably blow the weapon apart.

That's how you see heavier boolits going slower, usually with less powder than a light one in the same caliber.

Someone else can probably explain this better, but that's at least part of the general concept.

[bmortell]

as the projectile gets heavier it also becomes larger in volume, the extra volume goes further into the case since the outside specs is mostly fixed. so with smaller space for powder it takes less powder to make the same pressure. its also one way to judge a projectile design if say you find a 300gr 44 boolit that only takes up the same case space as a 250gr one that can be good

[RED BEAR]

A heavier bullet gives more resistance to burning powder causing pressure to increase. The pressure will build until there is a release.

[T_McD]

First off, I am not a ballistic expert nor a rocket scientist, but the above comments have it right I think. If you were to compare the pressures of max loads, you should find they are fairly close. Velocity will vary with bullet weight, but the bullets are generally subjected to equivalent pressures.

You can also use this to see when a powder becomes less than ideal for a given caliber, it may have safe loading data, but it isn’t at the same pressures as other powders. Meaning it wasn’t really designed with that caliber in mind.

[AllanD]

Another thing to consider, Most powders burn "progressively" meaning the more pressure there is the faster they burn and the faster they burn, the more pressure they make. It's a visious cycle until the bullet leaves the barrel or the structure of the barrel or breech fails

[Guncrank]

I know little about powder. When read the load data I have noticed that as the bullet weight goes up the grains of powder go down. I was wondering what am I missing because using logic knowing nothing about powder that seems to opposite what I as a know nothing person would think.

Grumpy1,

The gentlemen above have given you very good advice. But if you think of it this way perhaps the picture will become a bit more clear.
The relationship of an amount of powder in a given sized cartridge case, being held in place with a bullet of appropriate weight will allow you to see the following...
X amount of powder will, when burned, produce Y amount of gas volume. If the amount of gas volume produced is equal to the task of pushing the bullet weight/mass out the barrel of the firearm in question in the appropriate time interval, all is good and everyone goes home with a big smile. However, if X amount of powder can produce a volume of gas significantly greater than is needed to launch the bitter-pill down range then pressures inside the case and barrel will be greater than those systems were designed to contain for those few milliseconds necessary to push the bullet out of the barrel. And as may be seen all over the inter-web, it is in those few milliseconds when gas volume, from too large a charge of powder exceeds the ability of the brass case and steel barrel to contain it all, that very bad things will happen!

GC