Temperature Sensitivity of Old and New Vihtavuori N140 with .223 Wylde Service Rifles
During a study of temperature-sensitivity of powders for use in .223 Wylde high power service rifles, I came across a report that Vihtavuori N140 had been changed since I bought my last bottle in 2020. The new N140 was reported to have a decoppering agent and to be "temperature-stable" as indicated on the bottle.
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New Vihtavuori N140 on the left (Lot# 02.06.2021) and Old N140 on the right ( Lot# 01.12.2017)
Methods and powder charges used to generate the following graph comparing new N140 with old N140 and Varget are HERE and part of a larger study.
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*p<0.05 Significant temperature-induced increase in muzzle velocity, one-way ANOVA, Holm-Sidak multiple comparison.
There is also a significantly higher velocity (p<0.05) with new N140 by two-way ANOVA and Holm-Sidak multiple comparison.
The new N140 appears to be less temperature sensitive below 68F (20C) than the old. New N140 produces significantly higher velocity than the old at the same case charge with a 77 grain bullet. Both the new and the old N140 are moderately temperature sensitive above 68F compared to Varget. With a case powder charge of 24.3 grains, both the old and the new N140 at 129F (54C) produce overpressure signs on primers (primers flattened and partially extruded from the primer pocket).