WCChapin | More Kar98k Mauser Sporter – Hornady 170 RN with GRT Charges of IMR 4166 and 4064

Range time testing charges of IMR 4166 and IMR 4064 recommended by Gordon’s Reloading Tool.

A while back, 46.5 grains of IMR 4166 showed potential at 150 yards. I decided to chronograph a few charges in that area for evaluation. There seems to be a 2,600 fps plateau – it may be because the powder burnout occurs past the muzzle.

Based on the velocity data, the Optimum Barrel Time calculation in GRT predicts a node at 45.87 grains of 4166; behavior on target suggests that 46.7 grains may also be a region to explore. Autumn evening lighting and chromatograph accuracy/tolerance may be a consideration.

The parametric powder search in GRT (comparison with the 46.7 grain IMR 4166 charge) indicates that 47.0 grains of IMR 4064 would have a good barrel time, good case fill, and burnout just before muzzle passage.

1940 337 Gustloff Werke Karabiner 98 k – sporterized
Ru Ruhrstahl AG barrel blank
Geco finished barrel
Weaver bases / Leupold Rifleman rings / Leupold M8-4X scope

Gordon’s Reloading Tool https://www.grtools.de

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