Vihtavuori Powder Question

[Laurie]

Forget N150 and N550 for the 284 with 175gn and heavier bullets. These powders are markedly faster burning than burning rate charts and tables show. That's why they're widely used in 308 Win and even 223 Rem, the latter with heavier than 80gn bullets. In fact, forget / ignore burning rate charts completely for most Viht powders. At the very least, anything slower burning than N140 is shown as far too slow burning compared to the Hodgdon / ADI extruded / Extreme grades and IMR equivalents. (I've used N150 for over 20 years in 308 Win with 155gn class bullet weights and prefer it to N140, the more commonly used powder in this combination.)

N160 is also considerably 'faster' than the tables show, and is IME closer to the 4350s than 4831s. Despite what Viht says about its N100 and equivalent N500 grades having same burn speeds, N560 is considerably slower burning in practice than N160 though.

In the UK and Europe, N165, and probably to a lesser extent, N160 are commonly used in 284 and the Shehane with 175s and heavier (in properly throated chambers of course to avoid over-deep bullet seating). Until recently though, as in North America, H4831sc was probably the most popular choice among the few UK top national level 'Effers' who still shoot 284. (Few do now - the WSMs, 7mm and 300 are the norm here in F-Class league rounds.) However, as of 18 months ago, the importation of all non-Enduron IMRs and Hodgdon / ADI Extreme grades was stopped by new health & safety / environmental regulations. As people use up their husbanded stashes of H4350/4831/VarGet, they have to switch to European made propellants and Viht grades are a popular choice. The 284 case just holds enough N165 to achieve the favoured 2,820-2,850 fps speeds from 180s in a 30-inch barrel - mild to moderate charge compression is needed and a powder funnel with a longer drop tube like the 5.5" tubed Forster Universal Funnel is advisable. N165 has a huge plus in that it is a proven barrel life extender in numbers like the 284 and 6.5-284.

The new N555 is a tad faster burning than N160 it seems based on a simple desktop exercise I did comparing N550, N160, N560 charge weights and MVs for same bullets in the 10 or so cartridges Viht lists N555 loads for. In smaller cartridges, max charges are often marginally higher for 555 than 160 in fact, for others (30-06 and 284 Win) they're the same or a tad lower. Conversely, there is large gap between N550 and N555 maximum charge weights for these cartridges. N555 is a 'mild' powder compared to other Viht N500 series 'High-Energy' grades with a nominal 3,700KJ per 1Kg powder weight specific energy value - same as N140 in fact - compared to c.4,000 for the others. (Some used to be shown higher still and I suspect may be 'hotter' than Viht shows.) ALL N500 series powders have either been reformulated to be temperature stable or made as such from scratch in recent introductions - N555, N565, N568. How they now compare with say H4350 and H4831 I can't say - TS is much less of an issue in the British Isles than the US / Canada with our very temperate climate.

I have done a few exercises with some of these powders and they're either written up or will be shortly in Target Sports free online magazine.

A final point on N150 and even more so N550 and N160 - the default Ba values in QuickLOAD are WAY wrong (too 'slow') and predictions therefore seriously underestimate pressures / MVs.

http://www.targetshooter.co.uk/?p=3483

http://www.targetshooter.co.uk/?p=3609

http://www.targetshooter.co.uk/?p=3624

(Results for the outstanding 9 or 10 4350-alternative powders including N550 and N555 will be published shortly.)

 

[DE-F-Open]

Forget N150 and N550 for the 284 with 175gn and heavier bullets. These powders are markedly faster burning than burning rate charts and tables show. That's why they're widely used in 308 Win and even 223 Rem, the latter with heavier than 80gn bullets. In fact, forget / ignore burning rate charts completely for most Viht powders. At the very least, anything slower burning than N140 is shown as far too slow burning compared to the Hodgdon / ADI extruded / Extreme grades and IMR equivalents. (I've used N150 for over 20 years in 308 Win with 155gn class bullet weights and prefer it to N140, the more commonly used powder in this combination.)

N160 is also considerably 'faster' than the tables show, and is IME closer to the 4350s than 4831s. Despite what Viht says about its N100 and equivalent N500 grades having same burn speeds, N560 is considerably slower burning in practice than N160 though.

In the UK and Europe, N165, and probably to a lesser extent, N160 are commonly used in 284 and the Shehane with 175s and heavier (in properly throated chambers of course to avoid over-deep bullet seating). Until recently though, as in North America, H4831sc was probably the most popular choice among the few UK top national level 'Effers' who still shoot 284. (Few do now - the WSMs, 7mm and 300 are the norm here in F-Class league rounds.) However, as of 18 months ago, the importation of all non-Enduron IMRs and Hodgdon / ADI Extreme grades was stopped by new health & safety / environmental regulations. As people use up their husbanded stashes of H4350/4831/VarGet, they have to switch to European made propellants and Viht grades are a popular choice. The 284 case just holds enough N165 to achieve the favoured 2,820-2,850 fps speeds from 180s in a 30-inch barrel - mild to moderate charge compression is needed and a powder funnel with a longer drop tube like the 5.5" tubed Forster Universal Funnel is advisable. N165 has a huge plus in that it is a proven barrel life extender in numbers like the 284 and 6.5-284.

The new N555 is a tad faster burning than N160 it seems based on a simple desktop exercise I did comparing N550, N160, N560 charge weights and MVs for same bullets in the 10 or so cartridges Viht lists N555 loads for. In smaller cartridges, max charges are often marginally higher for 555 than 160 in fact, for others (30-06 and 284 Win) they're the same or a tad lower. Conversely, there is large gap between N550 and N555 maximum charge weights for these cartridges. N555 is a 'mild' powder compared to other Viht N500 series 'High-Energy' grades with a nominal 3,700KJ per 1Kg powder weight specific energy value - same as N140 in fact - compared to c.4,000 for the others. (Some used to be shown higher still and I suspect may be 'hotter' than Viht shows.) ALL N500 series powders have either been reformulated to be temperature stable or made as such from scratch in recent introductions - N555, N565, N568. How they now compare with say H4350 and H4831 I can't say - TS is much less of an issue in the British Isles than the US / Canada with our very temperate climate.

I have done a few exercises with some of these powders and they're either written up or will be shortly in Target Sports free online magazine.

A final point on N150 and even more so N550 and N160 - the default Ba values in QuickLOAD are WAY wrong (too 'slow') and predictions therefore seriously underestimate pressures / MVs.

http://www.targetshooter.co.uk/?p=3483

http://www.targetshooter.co.uk/?p=3609

http://www.targetshooter.co.uk/?p=3624

(Results for the outstanding 9 or 10 4350-alternative powders including N550 and N555 will be published shortly.)

Thank you very much for the very comprehensive response - much appreciated - lots to think about.

 

[DE-F-Open]

Many thanks to the many shooters who responded to my request for info - there's a lot of information to consider and it looks like many hours of testing to be accomplished, assuming I can find the various powders mentioned.

Thanks to everyone.

John

 

[whatwind?]

SW4350 is a slower version of H4350

 

[Ned Ludd]

Many thanks to the many shooters who responded to my request for info - there's a lot of information to consider and it looks like many hours of testing to be accomplished, assuming I can find the various powders mentioned.

Thanks to everyone.

John

Not to try and throw a stick into the works, but there is also the variable of powder energy content to consider. Burn rate is certainly a criteria shooters use to get to the right neighborhood with their powder choice for a given caliber.bullet weight. But as has been noted in the previous responses, advertised burn rates are not always accurate, and the burn rate charts don't take energy content into account. Some powders are clearly more energetic than others, and I'm solely talking about within the single-base powders at this point. If you choose a powder that has relatively low energy content, you may not be able to hit a comparable accuracy/precision window (i.e. node) that you can with another more energetic powder than has a very similar burn rate.

If you're really interested in testing a number of different powders within the H4350 burn rate range on the chart, that could be a huge amount of work depending on how you approached it, as you indicated. My suggestion to simplify that would be the use of a reloading program such as QuickLoad or Gordon's Reloading Tool (GRT). These programs can provide some information upfront about the energy content of various powders (i.e. in the powder files). They also allow one to obtain an actual velocity for a known charge weight of a given powder, then use that information to predict where the loads might tune in (i.e. velocity), and approximately where MAX pressure will be. I have done something similar to what you're describing a few times in the past. I purchased one pound only of 6-7 different powders within a given burn rate range, loaded up what I knew to be slightly reduced loads (i.e. "safe" loads), then determined actual velocity obtained with each powder. The use of QuickLoad then allowed me to rule out further testing with several of those powders, because they simply were not going to give me the performance I wanted. In fact, it is possible at times to rule out a potential powder simply by doing some in silico predictions with one of these reloading programs, if the predicted results are simply too far away from where you need to end up. Either way, whatever you can do up front to minimize the number of powders you have to obtain and how much testing obtaining a reasonable answer will require will likely be of significant benefit.

 

[243winxb]

http://www.adiworldclass.com.au/powder-equivalents/

 

[Reloder28]

N165

 

[DE-F-Open]

http://www.adiworldclass.com.au/powder-equivalents/

thanks