Powder burn rates.

[Jaco1234]

What does powder burn rate tell you?
2.7 grains of Bullseye, #14 on the burn rate chart, is a hotter load tha 7 grains of Trail Boss, burn rate #22.
So how does burn rate relate to performance? Wouldn't volume chang be a better indicator of performances. How does burn rate relate to chamber pressure?

 

[rockquarry]

What does powder burn rate tell you?
2.7 grains of Bullseye, #14 on the burn rate chart, is a hotter load tha 7 grains of Trail Boss, burn rate #22.
So how does burn rate relate to performance? Wouldn't volume chang be a better indicator of performances. How does burn rate relate to chamber pressure?

Burn rate can change depending on the cartridge and other factors like, as you mentioned, volume change. Burn rate charts are rough guidelines at best.

 

[yeti]

Burn rate charts are not directly related to Power Factor or load volume. There is a relationship, but it is not direct. Although faster powders usually require less volume to achieve similar results, the resulting pressure spikes may be less than ideal or even dangerous in some loads. The burn rate charts are estimations and offer limited help in selecting substitute powders. That being said, many of us do find the charts helpful.

Make sure the new powder is appropriate for the application. Correct tool for the job kind of thing.
Start low - based upon the manufacturer's specific load recommendations and work your way up, chrono testing and looking for overpressure signs as you go.

 

[mikld]

Burn rate charts used to be called "Relative Burn Rate Charts". Charts only show how burn rates relate powder to powder. One powder many be listed as faster or slower than another powder but not by how much. Should be used as reference only...

 

[DWalt]

Ballisticians use the term Relative Quickness (RQ) instead of burning rate. This is sort of an explanation. Relative Burning Speed of Smokeless Powders

 

[reddog81]

Burn rates have no relation to charges used. The burn rate chart can be used to determine other similar powders. You still need to find appropriate load data for each powder. Similar powders usually have similar charges but not always.

 

[The Norseman]

Subjective Ideas and Uses

Great thread and discussion.
The other chart I started paying attention to
is the Heat Index Chart.

When ever I’m researching a powder I
always look at the:
1 Relative Burn Rate Chart,
2 Heat Index Chart,
3 and is the powder a Single Base (nitrocellulose)
low energy or Double Base powder (% nitrocellulose
and % nitroglycerin) high energy.

For example:
IMR 4350 is #130, Heat Index is 3760 kj/kg
and Single Base powder

Vihtavuori N530 #100, Heat Index 4100 kj/kg
and a Double Base powder.

The V.V. powder is high energy and the rifle
barrel will not last as long and probably
good for long range hunting/shooting.

But that’s just me. I hope this is of use to
someone.

 

[taz666]

The chart is an indicator of how fast a given powder will achieve its peak pressure compared to other powders listed.

 

[DWalt]

It has to do with maximizing how effectively and efficiently the chemical energy (heat content) of a propellant can be converted into the kinetic energy of the projectile. A gun is essentially a heat engine, just as a gasoline car engine is. You can actually calculate the horsepower of your gun and load fairly easily. A typical .22 rifle is about 90 horsepower.

 

[Jaco1234]

Where an I find a heat index chart?

 

[jem102]

It has to do with maximizing how effectively and efficiently the chemical energy (heat content) of a propellant can be converted into the kinetic energy of the projectile. A gun is essentially a heat engine, just as a gasoline car engine is. You can actually calculate the horsepower of your gun and load fairly easily. A typical .22 rifle is about 90 horsepower.

Exactly. Also, I have never seen a heat index chart, thanks "Noreseman", but the more chemical energy released as heat per grain burned, your point, will (at least in theory) give you an increasingly more efficient/higher potential loading.
And as stated the heat increase has a price on barrel life. I have seen some X-course barrels go south in 3-4 thousand rounds from max charges of double based powders. They would still be OK for 200 yard work but not 300+.

 

[Nevada Ed]

Look up three different charts and you will see

that they list the powders in different burn rates !!

Data from the powder maker, is the best way to find out what
"Their" powder does, when learning about powders.

Even load data manuals have different amounts of pressues and powder
in their starting and full loads.

It does make for good reading with some head scractching.

 

[rwsmith]

Look at a powder.....

Look at a powder like 'Trail Boss'. It was specifically designed to be much bulkier than it 'needed' to be in relation to its burn rate and can fill up a cartridge without overpressure.

 

[SlamFire]

I believe a pressure curve (pick the standard cartridge) would be a better means of comparing powders, than some "burn rate" chart.

I also believe, the reason industry puts out a burn rate chart, is so we reloaders don't have good data to compare powders.

 

[The Norseman]

Heating up

Here are the Heat Index Charts I’ve
acquired.
I hope they can be seen ok and useful.

 

[The Norseman]

Heat Pistol Powders

Here’s the other one with Pistol powders.

 

[taz666]

Might be just me but what does the chart(s) have to do with powder burn rate The Norseman?

 

[Jaco1234]

Thanks Norseman.
The units, energy/mass, make more sense than mass/time, when comparing powders.

 

[jem102]

Very interesting charts. I am surprised at some of the numbers. I used a lot of H-322 shooting IHMSA and always considered it a mild powder but that chart listing may explain why my first 7TCU barrel wound up with rings in it. Thanks for the information.

 

[pantannojack]

I recall when Bullseye was rated #1 and WW231 #2 on the progressive burn rate chart. I believe pressure/heat has much to do with how propellant acts relative to cartridge/projectile, case volume, shoulder geometry, free bore ...