N568 Vihtavuori Powder
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CONatureBoy
Well-Known Member
QuickLoad says a 300 Norma Mag, SAAMI COAL, 26" barrel, shooting a Berger 230 OTM in front of a max safe charge of 91.6 grains of N568 achieves a muzzle velocity of 2,956 fps. QuickLoad also says a 338 Lapua Mag, SAAMI COAL, 26" barrel, shoots a Berger 250 OTM with 90.3 grains (uncompressed, 100.0% fill ratio, pmax 47,344 psi) at 2,727 fps, or 96.7 grains (compressed, 107.1% fill ratio, if that's even doable, which I doubt) at 2,944 fps. If you allow a COAL of 0.2" over SAAMI, that same 96.7 grains has a fill ratio of 101.4%, and you get 2,862 fps. Maybe that's doable. Switch to the 300-grain Berger OTM, and back to the SAAMI COAL, you have to get to 103.6% fill ratio to hit max safe peak pressure at 2,693 fps. Add 0.2" to the COAL, a 100% fill becomes 90.8 grains, which is well under safe pmax, but only yields 2,658 fps. I don't have (or load for) a Lapua, but I do have a 300 RUM. Maybe the heavy-for-caliber RUM N568 loads are as close to optimal as this powder can achieve, speed wise. As I recall it has a very uniform kernel shape; maybe the powder's virtue is that the kernel shape lends itself to very small extreme spread in the muzzle velocity, hence to extreme accuracy for target shooting. Otherwise, I must say this powder doesn't seem to have much to recommend it. I bought three kilos when I couldn't get anything else for my RUM. Glad to have a backup powder, but also glad I have a few pounds of other powders that promise state-of-the-art muzzle velocity. Speed does thrill.
CONatureBoy
Well-Known Member
I bet the Norma AI will do well with this powder. Hope you'll let us know. I think I'm going to try this powder with the 230-grain A-Tip: low ES plus an inherently accurate target bullet should make for some fun long-distance target shooting, at least. I'll post results as soon as my RUM comes back from the gunsmith with its new 1:9 twist barrel. . . .
DirtNap35
Well-Known Member
Requested load from VV, finally got it back.
6.5 PRC
Berger 156
N568
57.4
63.1 2985 fps 102%
N565
53.5
59.7. 2930 fps 98%
RL26
52.0
57.8. 2944 fps 90%
Retumbo
57.0
63.3. 2986 fps 106%
6.5 PRC
Berger 156
N568
57.4
63.1 2985 fps 102%
N565
53.5
59.7. 2930 fps 98%
RL26
52.0
57.8. 2944 fps 90%
Retumbo
57.0
63.3. 2986 fps 106%
CONatureBoy
Well-Known Member
I just got the QuickLoad data update that includes N568. If anyone would like to see its calculations for a given caliber and bullet, please let me know.
CONatureBoy
Well-Known Member
Fast as Retumbo looks pretty good!
DirtNap35
Well-Known Member
I would imagine running 58.4 grains of N570 is really compressed. Keep in mind N568 is essentially a short cut version of N570. Also the above was done by capstone at 2.955 OAL
CONatureBoy
Well-Known Member
N568 has about 4% less energy by weight than N570, which I suppose explains why you need more N568 to approach N570 velocities in many calibers. I wonder if N568 shines in calibers we used to call highly overbore, where filling the case with a higher energy powder (even a slow powder) would produce too much peak pressure?
