Hi If I am loading a 300 Savage or a 22-250 how do I know what burn rate of powder I want with out checking for load data.
Which of course I do!!!!!!!!!!!!!!check the book for load data before doing anything .
Is speed of the bullet the total factor involved, with burn rate?
what has burn rate got to do with the delivery of the bullet from one calibur over the other calibur. It seems some what confusing which goes right along with the reloading subject.In fact its a confusing question to ask.
Thanks as always I do appreciate your help , how else can one learn.
Bill

Bill,

I think there are a few factors at work regarding what speed powder works best in a given chambering, and also be aware that burn rates change somewhat between chambering for differening powders.

I'd say the main factors are the expansion ratio of the round: ie volume of the case to bore size, a bigger case for a given bore needs a slower powder, the opperating pressure of the round, higher pressures generally prefer slower powders, and the bullet weight for a given bore, heavier bullets generally favor slower powders.

Speed is related to the larger cases in a given bore being able to burn more powder and hence sustain a high pressure for a longer amount of time while the bullet is accelerated on it's way down the barrel. Slower powders by themselves don't produce higher velocities, it is a large case that is capable of allowing a slow powder to reach peak pressure and maintain it that produces high velocities.

Thanks Paul H. A very informed reply.

Paul gives a good explaination. Slower powders also allow you to use 100-105% load density which can often enhance accuracy. I use IMR7828ssc in my .260ai. By using a drop tube I can get 48gr under a 142gr SMK (compressed load). This leaves no space for the powder to shift & the vel. are very uniform which helps w/ accuracy. Pressures are also lower for the given vel. than if I used a faster powder like IMR4064.

Some good replies here. I was wondering if I could hijack this thread for a quick second and ask what kind of test do they do to determine how fast the powder is?

Just light a grain on fire and measure the "flash" time or what? I would be very intrested to find out.

Sorry for the hijack

quote:

Some good replies here. I was wondering if I could hijack this thread for a quick second and ask what kind of test do they do to determine how fast the powder is?

Just light a grain on fire and measure the "flash" time or what? I would be very intrested to find out.

The Vihtavuori manual claims the powder is tested in a "manometric bomb" which allows the burn caracteristics to be studied in a sealed chamber.
How it works is beyond me....

quote:

Originally posted by bill r:
Hi If I am loading a 300 Savage or a 22-250 how do I know what burn rate of powder I want with out checking for load data.
Bill

Smokeless powders all deliver the same amount of energy per grain of powder, under ideal burn circumstances. So when you look at the reloading manual you will see that some powders with a slower burn rate will allow you to use more grains of powder, which in turn gives more energy to the bullet and a higher velocity.

On the other hand, depending on case capacity vs. bore diameter, a certain slow powder may not get enough resistance from the bullet to reach a high enough burn temperature for complete ignition, thus potential energy is not realized.

For example, 10 gr of Unique under a 210 gr bullet makes a nice load for my 41 magnum revolver. While 10 gr of H870 has the same amount of potential energy as 10 gr of Unique, H870 will not perform in the revolver because the burn rate is so slow that it will never develope the pressure or temperature to completely burn.

You will see in the load manuals each cartridge has a wide range of powders suitable for use. The higher the ratio of case capacity divided by bore diameter, the slower the powder must be to take advantage of the case volume without causing excessive pressure.

As a second example, H4831 is a fairly slow powder and is very suitable for loading the 270 win to max velocities with a 150 gr bullet.

The 270 with this bullet may also be loaded with an extremely fast powder such as Blue Dot, but only in very small amounts, which will yield a low velocity, light recoiling load. If one attempts to put enough Blue Dot into the 270 to make the 150 gr bullet run to 2800 fps, the pressure will build so rapidly, before the bullet has time to get out of the way, that the rifle will be destroyed.

The best advice is to go to the reloading manual, turn to the page for the cartridge of interest, and select one of the powders which give nearly 100% load density with the velocity you are interested in.

Considering that both of the cartridges you listed are rather forgiving in their choice of powders, IMR 3031 works well in both, even though it might not be considered ideal for either.