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.