'Burning rate' isn't a fixed metric, so comparisons are at best approximate, and on occasions downright misleading. Not only does it depend on the exact testing method used by the various producers, but as is often pointed out (and equally frequently ignored by handloaders) relative burning rates can (and often do) change depending on the application, ie cartridge and bullet weight. Taking an easily found and current example, look at various suitable cartridges' loads data using Hodgdon's online Reloading Center facility for the same bullets (in a cartridge) with H4350 and IMR-4451. Maximum loads (with associated MVs and pressures) regularly change their relationships depending on the cartridge - that is the IMR powder say is allowed higher charges producing more or less same pressures than the Hodgdon equivalent in cartridge A, but the positions are reversed in cartridge B with a larger or smaller case capacity to bore ratio.
Europe has (as per the US) suffered major and sometimes lengthy absences of H. VarGet in recent years, on one occasion there being no new deliveries for 18 months or so and a lot of desperate users. While VarGet famine was at its worst, the importers of Czech manufactured Lovex powders turned up with a new to us grade called SO65 and in the Lovex material it was shown on the same horizontal line as H. VarGet in the relative burning rate chart. A lot of people rushed out and bought it to replace their missing favourite propellant. It simply didn't work in classic H. VarGet applications. I was give three tubs later FOC by a guy in our guntrade and he refused to take a penny saying it was 'worthless' and if I wished to waste time, bullets and barrel life on proving it to myself I was welcome. A bit of research and look at Lovex's loading data soon showed up some key features - like it has a substantially lower specific energy value than VarGet, so you need more of it in the charge to produce the same MVs. Whilst QuickLOAD showed the pair having a similar specific density rating, in practice SO65 is bulkier and looking at Lovex's 308 Win data, it is obvious that maximum loads in all bar the heaviest bullet quoted were determined by case capacity, not reaching maximum pressures. Then managing to find it in a German produced burning rate chart, it was shown several lines lower (slower burning) than the Hodgdon product - which didn't surprise me a bit after some playing with it. SO65 turns out in fact to be an excellent and consistent performer in cartridges like 7X57mm and 7X64mm whose cases are relatively roomy and which need slower burning powders than 308 Win. I use it in light short-range loads for a 7mm-08 Rem F-Class rifle and it shoots one-hole at 100 and apparently produces pretty well the same precision levels at 200 and 300 over extended shot series in matches.
The message isn't just that the manufacturer's positioning of its products in a scale of things may be incorrect, but that other factors +(density and energy) may affect its utility and performance as much as relative burning rate or even more so.
FWIW, in everything I've used the pair for over the years (308 Win + various; 223 with 80s-90s; 6BR with 90s to 107s) Re15 is always a bit slower burning than h. Varget, but in some cases can be loaded to charge levels that give usefully higher velocities ...... provided there isn't going to be an ambient temperature issue as Re15 is badly affected by high temperatures.
As another insight into this complex and often confusing issue, I was looking something else up in an old copy of the Norma Reloading Manual, a rather out of date edition (2004) as we lost Norma powders in the UK a generation ago (but they are apparently reappearing now) and reacquainted myself with a very unusual burning rate table. Rather than have the usual numbered fast to slow list or (the better) table with manufacturer columns and common burning rate horizontal lines, Norma has adopted a different approach - relative pressure and MV results from a single loading in a single cartridge using common components, in this case 308 Win with a single powder charge weight (43.2gn) and a single bullet (143gn FMJ) and everything else in the mix the same bar powders. IMR-4350 was chosen for the base with the pressure and MV it produced valued at a base 100.00 and everything else shown against them.
Unfortunately, this table doesn't include H. VarGet. It does have H4895 which is usually rated as marginally 'faster' than Varget by everybody else.
H4895 was rated at 127.5 relative velocity and 171.0 relative pressure where high = 'faster burning'.
Re15 / Norma 203-B were 120.0 rel velocity + 133.6 rel pressure
a very large pressure differential indeed.
A number of interesting things come out of this 'real life' way of showing burning rates. For instance, Vihtavuori (which I would consider as being gold standard in its data and methodology) always quotes the N100 series powders which have 'high-energy' N500 series offshoots as having the same burning rate, whereas handloaders' actual experience suggests that infusing nitroglycerin into the 100 series powder makes the 500 version considerably slower burning in some grades. The Norma table supports this.
N140 v 540 MV ................. 125.5 v 119.3
N140 v N540 Pressure ....... 157.3 v 137.5
N150 v 550 MV ................. 115.7 v 111.2
N150 v 550 Pressure ........ 118.0 v 112.6
N160 v 560 MV ................. 102.1 v 91.1
N160 v 560 Pressure ......... 107.5 v 83.2
As the Norma text explains, these results may be (likely will be) different if a very different cartridge + bullet combination were chosen - eg the over bore capacity 7mm Remington Magnum and heavy 175gn bullet.
In many burn rate charts, Varget is shown to be "faster" than Re 15; however others have Re 15 faster. I use both in my Dasher....so I decided to go out on this cold day and chronograph (Oehler 35) each. I chose 33.0 gr. of each and shot the 105 gr. Bart Gungnir in a 28 inch Brux 4-groove barrel. The Re 15 registered 2921 fps and the Varget @ 2976 fps. Although this is not conclusive it confirms my findings of a few years ago. I know that different lots show variations, and I will test these again. Good shooting....James
