Why different powder load weights (grains) ?

[Aprilia Man]

Hi Guys,

Just want to get some answers. Been checking out some powder load weights (grains) on different brands of powder, why is it that each brand suggests different weights (grain).

For example on .45 ACP with LRN bullet 230 gr

Titegroup = (4.0 gr start and 4.8 gr max)

Winchester 231 = (4.3 gr start and 5.3 gr max)

Bullseye = (4.3 gr start and 5.7 gr max) ........

........... and so on. I've seen a lot of data and every brand has a different suggested loading.



Why is that?

 

[sniper58]

different powders have different burn rates. Max pressure will be reached earlier with different powders.
The construction of the bullets can affect pressure as well. Always follow the recommendations in you reloading manuals.

 

[Slopok]

Im guesing that some burn hotte/faster than others. I noticedthe samething with varget and H335. That or on powder is more dense then the other? Im not 100%, but that's my theory.


Edit: Sniper58 beat me to it.

 

[SavageLapua]

There are MANY reasons for different charge weights. Like sniper58 said, "different powders have different burn rates. Max pressure will be reached earlier with different powders. The construction of the bullets can affect pressure as well". Other reasons include the granule shape, such as spherical, cylindrical, flakes, etc. The larger the surface area, the slower it's burn rate. Chemical make up also contributes to burn rates. Generally, slower powders are meant for long barrels, big bores and heavy projectiles. The faster for longish barrels and small bores. And of course pistols generally utilize the fastest powders. Should also mention that typically, slower powders are more stable as far as temperature variations and pressure spikes are concerned.

Chuck Hawks has a pretty good explanation on his site (Chuck Hawks). You should also be able to read up on this in your Reloading Manual.

The Hodgdon site has a "Burn Rate Chart". Hodgdon

SL

 

[bigedp51]

Below is from Exterior Ballistics by Sierra


Modern smokeless propellants usually fall into one of two basic categories; single base and double base. These designations describe the chemical makeup of the propellants, with single based powders being comprised primarily of nitro-cellulose, and double based powders being made up of a combination of nitro-cellulose and nitroglycerine. Both types are still in widespread use today and are produced by a variety of domestic and foreign manufacturers. There are triple based powders as well, but these are limited almost exclusively to military applications and are virtually unknown among reloaders.

Within the two primary categories, single and double based, there is a wide variety of powder types, defined by geometry or shape. Some of the most common types in use today are flake, extruded tubular, and ball or spherical propellants. Regardless of the type of powder being discussed, its suitability to a given task is determined by its burning rate. Whereas black powder’s burning rate was controlled to a very limited degree by granulation, smokeless propellants are produced in a wide spectrum of burning rates. The IMR series of powders, for example, is a family of powders that are chemically very similar. Their fast burning powders such as IMR-4227 will produce virtually the same amount of gas volume and energy as their slow burning powders, such as IMR-7828. The real difference here, is the amount of time over which the powder will release its energy. Despite their chemical similarity, the burning rate of these powders can be controlled to suit the needs of a small case calling for a very “fast” powder, or a large magnum type case calling for a very “slow” burning powder. Aside from very minor chemical differences, the burning rate of the various powders is largely controlled by the size and shape (surface area), and the use of deterrent coatings such as dinitro-toluene (DNT). These charges are applied to the kernels of powder in varying degrees to control the burning characteristics of the finished product.

http://www.exteriorballistics.com/reloadbasics/powder.cfm