Relative Burn Rate Charts. . .

[STEEL SLINGER]

Relative Burn Rate Charts, which is the most accurate and up to date? I have seen several different burn rate charts from Hodgdon, Hornady, Nosler Handloader.com along with a few others and none of them are inline with one another. Some are close in some aspects and way far apart in others. There are a lot of new powders out on the market these days too, I would like to know were they fall in the scope of things. I'm not trying to reinvent the wheel, but there are some new spokes that could help the wheel go round better. Thanks for any input.

 

[fiftybmg]

Not the newest, but the most comprehensive I have found.

http://gsgroup.co.za/burnrates.html

 

[MagnumManiac]

Relative Burn Rate Charts, which is the most accurate and up to date? I have seen several different burn rate charts from Hodgdon, Hornady, Nosler Handloader.com along with a few others and none of them are inline with one another. Some are close in some aspects and way far apart in others. There are a lot of new powders out on the market these days too, I would like to know were they fall in the scope of things. I'm not trying to reinvent the wheel, but there are some new spokes that could help the wheel go round better. Thanks for any input.

One major problem with burn rate charts.....is that burn rates are NOT constant from cartridge to cartridge AND, some powders BEHAVE differently in certain case shapes/bore sizes/expansion ratios.
In fact, in certain cartridges/cases a powder that is one step faster produces higher velocities with less powder than the slower powder does.
Typical examples are RE19 and RE22, in a few cartridges and bullet weights, they switch where RE19 behaves slower than RE22. Prime examples are in 30-06 and 338WM. Many believe this is due to 'performance' of the powder, but in fact it is the BEHAVIOUR of the powder in this expansion ratio.
These are not the only powders that do this.

I would take burn rate charts as a very BROAD UNSCIENTIFIC GUIDE ONLY.
No 2 manufacturers have a 'standard' that all other powders are matched to. IMR rate 4895 with a RQ (Relative Quickness) number of 100, all other powders are compared to this, faster get a lower number, slower get a higher number.
Hodgdon uses a different powder as a baseline, as do Winchester etc, etc.
So trying to answer which is the most accurate....your guess is as good as mine.
I look at the top 3 powders giving the highest velocities, these are generally the most EFFICIENT in that case size.
This a very good rule of thumb to go by when choosing a powder.
Hope this helps.

Cheers.

 

[ShtrRdy]

I've wondered about this too at times. There must not be an industry standard way to measure the capability of a given powder/propellant. I suspect Temperature, pressure, Volume, and maybe Humidity factor into how a given powder reacts. I suppose the way the powder is ignited could influence the test too.

MagnumManiac posted as I was typing. I agree with his points.

 

[Hand Skills]

It's true, burn rate is just one characteristic. I have seen a couple of different 'units' used to measure burn rate, but 'relative' burn rate charts seem to be most available. Given lot to lot variances and differing expansion ratios powders can easily 'change places' on the relative burn rate chart, but it does offer a place to start.

The other two characteristics I consider when choosing a powder are energy density, (usually in kJ/kg) and bulk density (usually relative - how many grains fit in a given case or volume). These stats are harder to find, and more often a dynamic model like Quickload can be very helpful for predicting how different powders will behave in a given set of conditions (cartridge, bullet, OAL, case capacity, barrel length etc.).

RL-26 is a good example. It's listed as slower than H1000. However, it has a significantly higher energy density as well as a higher bulk density. RL-26 works really well in a .270win with 140-150gr bullets. Even though H1000 is a faster powder, with its low bulk density and low energy density, I can't fit enough of it in the case to create optimal velocity. In fact, RL-26 behaves a lot like IMR7828ssc in the .270 a which resides quite a few spots up the burn chart.

 

[J E Custom]

The main thing to understand about burn rate charts is that even though a powder falls just above or below another powder, the burn rate is not linear. It may be very close to the next powder or very far away from the same burn rate.

So if you want to increase or decrease the burn rate you must/should
start at the lowest charge with the new powder and work back up. As stated, powders react differently in different case volumes ( I have a 7/08 and a 7/08 AI and they produce different pressures and velocities with the same powder and charge weight. they also produce different pressures and velocities while fire forming using the standard 7/08 load in a larger chamber (7/08 AI) than in a 7/08 SAMMI chamber.

Also even though the powders are in the same burn rates they can be slightly different so when you substitute one brand for another in the same burn rate, It would be prudent to reduce the load weight slightly to compensate for the difference.

J E CUSTOM

 

[Mike 338]

Burn rates are not even consistent between lots of the same powder so those charts are strictly ballparking.