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Thread: Comparison of Viht N-140 and Norma 203-B

  1. #1

    Comparison of Viht N-140 and Norma 203-B

    Good morning!

    Having caught the bug, I'm researching the reloading project after the next, which is 7x57R with a 150gr bullet. The only manufacturer data I've found is from Norma, which is fine, but they don't list Viht N140 as a powder in their data, which is what I'd like to use. This is because I already have a load of it, but more to the point I'm planning to develop a suite of rounds in 7-08 and 7x57R that use the same powder and bullets for the sake of economy and consistency. Once that's developed, I'll leave it at that and get on with some actual proper shooting!

    Anyway, back to Norma, who do recommend a minimum of 39gr of Norma 203-B and a maximum of 41. Now from the burn rate chart, and I know that's only a vague guide, Norma 203-B and Viht N-140 seem exactly the same. I realise that there are other things in play here and that one shouldn't assume direct substitutability, but I just wondered whether anyone here had had the opportunity to compare the two and what they'd concluded.

    Thanks!

  2. #2
    Rather than using a burn rate chart for comparing powders from different manufactureres, I'd use this:

    7 x 57R - Rifle reloading - Reloading Data - Vihtavuori

    I would compare N150 starting loads for 140gr Nosler and 160gr Sierra, then compare 140gr Nosler starting loads for N140 and N150.

  3. #3
    Have you looked at this VihtaVuori guide http://www.vihtavuori.com/en/reloadi...g/7-x-57r.html
    They list loads for 140 grain and 160 grain bullets with N140 so it shouldn't be hard to work up a load with 150grn bullets.
    It's the calibre of the shooter that counts not the calibre of the rifle.

  4. #4
    Quote Originally Posted by 8x57 View Post
    Have you looked at this VihtaVuori guide http://www.vihtavuori.com/en/reloadi...g/7-x-57r.html
    They list loads for 140 grain and 160 grain bullets with N140 so it shouldn't be hard to work up a load with 150grn bullets.
    I suppose I've been starting my research for these things with the bullet weight rather than the powder. 7x57R tends to be loaded with heavier bullets, and it looks from the data that I've been gathering like most loads for these use slower powders than N140. The 160gr Sierra SPBT doesn't have a"recipe" using N-140 for instance. That said, everything I see seems to point at something like 38-41gr of N140 for a 150gr bullet, which is about the same as for 7mm-08, which is the overlap that I'm looking for. That's also what the Norma data says for 203-B of course.

    I need to stop worrying about data. It's clearly somewhere between 38gr and 41gr and N140. I'll start at 37 to satisfy my nerve, that's all.

  5. #5
    where are you getting norma powder?

  6. #6
    I'm not, I just have the data, just wondering how relevant it is to an N140 load.

  7. #7
    Norma powders are made by Bofors in Sweden and are not available in the UK to handloaders. Well, not at least in Norma tins. However, since Bofors makes most Alliant rifle powders, the same thing or something so close as to be nearly indistinguishable is available here under a different name. In this case, 203B and Alliant Reloder 15 are so close to be the different production lots of one powder.

    QuickLOAD says that Norma's 41.0gn maximum load produces just under 2,600 fps at just over 44,000 psi PMax, and Re15 does almost the same thing with 10 fps and under 1,000 psi max pressure difference. CIP PMax for the 7X57R is 3,400 BAR / 49,313 psi.

    I say that Re15 is available here, but it may be difficult to find as many frustrated H. VarGet users have switched to it given the latter's no-supply for over 12 months. Using burning rate charts comparisons to find substitutes is often misleading, occasionally downright dangerous. At the very least, it's comparing only one characteristic out of several, and it's not a fixed value - the real burning rates of a selection of propellants can change in realtion to each other, even be reversed in different cartridges due to the effects of different fill-ratios and expansion ratios. The other big factor that those who rely too much on burning speeds forget or ignore is specific energy as the amount of energy and hence ultimately pressure in the chamber is a straight multiplication of the charge weight * specific energy which nowadays is provided KJ / Kg and in imperial days was BThu / lb. Handloading powders specific energy vary between ~3,650 KJ/Kg to getting on for 4,200, so 50gn of the latter dumps a great deal more energy into the case than the same weight of the former and has a big effect on pressure despite what burning rate comparisons might suggest.

    Personally, I'd say that Re15, N203B, and N140 are all a little faster burning than I'd use in the 7X57 family preferring powders around 4350 burning speeds with 150gn and heavier. However, QuickLOAD says they'll all work. 41gn N140 is predicted to produce 2,588 fps at 47,420 psi around 3,000 psi up on the Swedish pair and not far short of the cartridge's modest PMax (dictated by weak break-open shotgun type actions). If you're using a conventional bolt-action, you can safely run a lot higher anyway. I'd recommend slower burning Viht N150 instead though which uses a larger charge and gives a higher fill-ratio which is desirable. It's readily available, and is a very docile powder in this sort of application unless you force loads up too much. QuickLOAD says 44.0gn produces the same sorts of pressures as 41gn N140 / Re15 etc but improves the charge burn to nearly 100% and gives you an extra 30 fps MV, not that that's a great issue in this case. This would be a near maximum charge and working up from 40gn would be very advisable. One benefit of N140 or N150 over 203B / Re15 is that Viht powders burn more cleanly. I invariably find that high-energy Re series powders leave a great deal of black muck behind despite their burning at higher temperatures due to their nitroglycerine content - the opposite of what you'd expect. This is more an issue for target shooters with their long strings of shots, but why use a dirty burner in anything when there are cleaner (and in this case cheaper too) alternmatives?
    Last edited by Laurie; 17-09-2014 at 09:45.

  8. #8
    Thanks Laurie, that's a very comprehensive answer indeed! I know N140 isn't quite ideal for this load, but as you say, it should work fine, so I'm going to stick with that and my plan to essentially shoot the same round from all my rifles. I may yet see the error of my ways of course and move t N150, we shall see. Your point about the VV powders being clean burning is a good one.

    The 7-08 rounds I had loaded by HPS once used N150, and they really weren't that good in my rifle, certainly not as good as my own ones using N140. It may be to do with the short barrel, not sure. I wouldn't have thought it's because of load consistency coming from a company that specialises in loading custom target ammunition.

    Of course, I don't actually have the 7x57R drilling yet, but I'm tantalisingly close to having both the paperwork and the cash...

  9. #9
    Quote Originally Posted by Pine Marten View Post
    Thanks Laurie, that's a very comprehensive answer indeed! I know N140 isn't quite ideal for this load, but as you say, it should work fine, so I'm going to stick with that and my plan to essentially shoot the same round from all my rifles. I may yet see the error of my ways of course and move t N150, we shall see. Your point about the VV powders being clean burning is a good one.

    The 7-08 rounds I had loaded by HPS once used N150, and they really weren't that good in my rifle, certainly not as good as my own ones using N140. It may be to do with the short barrel, not sure. I wouldn't have thought it's because of load consistency coming from a company that specialises in loading custom target ammunition.

    Of course, I don't actually have the 7x57R drilling yet, but I'm tantalisingly close to having both the paperwork and the cash...
    Such faith does you credit PM but frankly I’d ‘park’ that experience and build on the success you’ve clearly achieved to date with your home reloading setup.

    Another point notwithstanding the powder you finally settle on must surely be what - other than determining the “sweet spot” charge - have you done in your reloading process to significantly influence the improvement in group size and consistency?

    The answer I fear will not be liked by a number of members who’ve made it very clear they consider the seeking of a rifle’s optimal OAL (base - orgive) to achieve improved accuracy a waste of time.

    What did you finally settle for by way offset from lands?

    Cheers


    K
    The enemy of knowledge is not ignorance, it is the illusion of knowledge.

  10. #10
    Quote Originally Posted by Klenchblaize View Post
    Such faith does you credit PM but frankly I’d ‘park’ that experience and build on the success you’ve clearly achieved to date with your home reloading setup.

    Another point notwithstanding the powder you finally settle on must surely be what - other than determining the “sweet spot” charge - have you done in your reloading process to significantly influence the improvement in group size and consistency?

    The answer I fear will not be liked by a number of members who’ve made it very clear they consider the seeking of a rifle’s optimal OAL (base - orgive) to achieve improved accuracy a waste of time.

    What did you finally settle for by way offset from lands?

    Cheers


    K
    K, you're going to land me in trouble again, I almost had my virtual head bitten off last time this topic was raised. I stuck to my guns, but was completely prepared to accept failure and change my ways should it be necessary. Only the thing is that it worked just fine. The only conclusion I can draw is that it worked just fine in my specific rifle, not that it's a general rule.

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