Powder burn rates

[spudgun]

I have a question.

Will a powder that burns at a slower rate be able to used as a subistute for a faster burn rate.

I am thinking of using H4831 in place of H4350.

Will it work?

Yes I know I must start low and work up.

 

[Ned Ludd]

It is not uncommon for people to test both H4831sc and H4350 in appropriate cartridges, and use whichever gives the best precision. It is certainly worth a try. You didn't mention the cartridge you're using, but you might consider trying short cut (H4831sc) if case capacity might be an issue with H4831.

 

[Texas10]

If we're talking about a 6.5CM, H4350 and H4831SC are two very good charges to use with 135, 140, 142 gr bullets.

 

[cptjack]

4831sc mor accurate than h4350 in 270

 

[spudgun]

It is not uncommon for people to test both H4831sc and H4350 in appropriate cartridges, and use whichever gives the best precision. It is certainly worth a try. You didn't mention the cartridge you're using, but you might consider trying short cut (H4831sc) if case capacity might be an issue with H4831.

I was thinking .224 valkyrie

 

[Ned Ludd]

I think the burn rates of your powder choices are too slow for the Valkyrie. The reloading data at Sierra lists powders with burn rates that mostly fall close to Varget. Not sure you'd even be able to get enough H4350 into the case.

https://sierrabullets.files.wordpress.com/2018/03/224-valkyrie1.pdf

 

[jr600yd]

I stumbled on this by mistake but it sure did work. Depending on cartridge sometimes H-4350 is a little to fast and H-4831a little to slow. Try AA-4350 the burn rate falls between those two. Shoots 107SMK’s out of my 6XC like a match made in heaven.

 

[shoot4fun]

I am with @Ned Ludd on powder choice. For 80-90 grain bullets I'd leave the H4831, even the short cut version, alone and look for powders such as Alliant 2000-MR, Varget, CFE-223 and RL17. I know RL17 and 2000MR fall very near H4350 on the burn rate chart but that is deceiving. Burn rate is not the sole aspect of a powder for making good choices. How a powder produces pressure is a big part of the equation and my experience with those two say they have a much broader usefulness in many cartridges (large and small capacity) than H4350 and most certainly H4831.
Again, just my two cents. I am not a chemist or physicist.

 

[Laurie]

Burn rate is not the sole aspect of a powder for making good choices. How a powder produces pressure is a big part of the equation and my experience with those two say they have a much broader usefulness in many cartridges (large and small capacity) than H4350 and most certainly H4831.

Amen to that sir! Simply far too much weight is placed on burn rate charts. Their data have to be treated as the very broadest of categorisations. ..... and that's before you start comparing charts from different sources which can move a powder grade up or down several steps.

Have a look at the chart here:

https://www.norma-ammunition.com/en/ammo-academy/Reloading-Data/

whose values were obtained by taking an actual cartridge (308 Win) and load-combination (143gn FMJ bullet / 43.2gn charge weight of each powder) then ranking them against IMR-4350 for both MV and pressure. In many cases, this method gives very different results from those based on 'closed bomb' lab testing. Viht N150 and 160 for instance end up in very different positions from those in Viht's chart, very much faster burning compared to the 4350s (N150) and IMR-4831 (N160).

That's not to say this result is better or more valid than others, but is a good measure of the large variations that regularly turn up with this metric.

For the OP, the answer to his question isn't whether a slower burner is better than another faster variation - whether it is or isn't is simply down to how well either matches the cartridge's characteristics, these primarily determined by the ratio of case volume to bore area and further modified by bullet weight. As Ned Ludd says I'd expect both to be too slow burning / bulky for the 224 Valkyrie in which case 4831 becomes even less well suited to the cartridge than 4350. Note in Sierra's 90 and 95gn tables (the heaviest bullets which therefore need relatively slower burners, the quartet that give the highest MVs are all dense high specific energy grades - three ball type powders and Alliant Re17, whose relative burn speed is usually reported somewhere close to that of IMR-4350, but which has smaller kernels allowing more to be packed into the case and contains considerably more potential chemical / heat energy than the venerable IMR grade. It is also one of Nitrochemie's unique 'EI' infused deterrent grades which tend to behave equally uniquely in actual loads combinations.

 

[XTR]

Is Re-17 stable enough to use in a competition rifle? I seem to remember it from some of the early heavy bullet experiments in F-TR as being one that could achieve good velocities, but much like Re-15 in that it might shoot awesome today but change temp 15F and the pressure spikes and the load falls apart.

 

[Laurie]

Is Re-17 stable enough to use in a competition rifle?

I'd have to say I too would have my doubts about it in this cartridge. I've been struck many times how Re17 / Reload Swiss RS60 shows up really well in an amazing number of QuickLOAD charge runs for a larger range of cartridge types than just about any other powder on the market. A real amazing do-almost-anything product were this true.

The proof of the pudding is in the eating as they say and I simply don't see or hear of real-life competitors using the powder in all these varying cartridge designs. It has its fans sure enough, but for use in just those cartridges where you'd expect it to do well - 6XC with 105gn and heavier bullets, 284 Win and others with similar capacity to bore ratios.

The temperature issue is one that bothers us in the UK a lot less than for you as we rarely see large temperature swings, but even so this powder seems to have a tendency to give fantastic velocities and precision for a while then for the latter to 'go sour' for no apparent reason. Given the precision demands and levels of competition in F-Class, Benchrest competition and similar, this variance / inconsistency is likely relative, and I believe Re17 remains an outstanding propellant for many hunters looking for maximum MVs from short magnums and other suitable cartridges. Equally, when I shot the 6XC, I never found a better powder although I tried hard enough. It simply proves though there is no single does-everything product.

 

[Zero333]

Playing around in Quickload, looks like around 29 gr of H-4831sc would be near max with 90 gr bullets.
Depending on COAL & bullet brand, 29 gr H-4831sc will generate between 44,000 psi (2.400" coal w/ 90gr SMK) and 56,800 psi (2.260"coal w/ Berger VLD).