Harrison on the .30-06.

Col. E.H. Harrison (USA, Ret.) left us a treasure trove of data from his cast bullet explorations. Some of the highlights gleaned from his experiences are:

Decisive factors in cast bullet success:

1. Bullet hardness: Alloy used in light loads should have a BHN of 10 or better. Heavier loads require at least BHN 20. Inadequate bullet strength = failure.
2. Bullet dimensions: Caliber .30 driving bands should measure .308" to .311". The nose diameter of bore-riding designs should be between .300" and .302".
3. Correct powder charge: Proven loads for standard weight bullets in the .30-06 include:

#2400 13 to 20 grains
IMR 4227 14 to 22 grains
4198 20 to 25 grains
4895 30 to 38 grains.

A maximum cast bullet load in the .30-06 can generate up to 30,000 psi, for 2200 fps. The 170 grain Lyman U311291 over 38 grains of IMR 4895 is getting close.

Attainable accuracy goals:

Light target loads: average 5 shot groups of 1.25" at 100 yards.
Medium power loads: average 5 shot groups of 2.00" at 100 yards.

Full power loads remain a work in progress.