Analysis of a Load: 60 gr. N120 / Barnes .458 45-70 300 grain 45-70 Semi-Spitzer

Though time-consuming to compile, I thought it might be of some interest to compile all the information I could on one specific load. The Savage 10ML-II load chosen is my current favorite, 60 grains by weight of Vihtavouri N120, Winchester 209 primer, MMP orange .50-458 sabot, RW .033” ventliner, and the Barnes "Original" .458 300 grain Semi-Spitzer.

Base Values

Pressure Max. = 27633 PSI.

Barrel time, from 10% of pressure max, to muzzle: 1.248 millisenconds

Calculated muzzle velocity: 2215 fps.

Observed, chronographed velocity: 2287 fps, 500 ft. above sea level, 82 degrees F. (5 shot string).

93.36% propellant burn.

3269 fpe @ muzzle.

Muzzle pressure: 3644 PSI.

18.67 ft. / lbs. recoil at bullet exit, .101 in. gun travel.

Greenhill’s twist required = 73.6 calibers (33.7 in.)

Lethality Values

Hatcher’s RSP = 120.4

A-Square Penetration Index = 41

A-Square Shock Power Index = 539

Tappan’s WAVE factor = 120.4

IPSC Power Factor = 665

Lott’s Estimated Effective Energy: EEE1=306 EEE2=1497

Taylor Knock-Out Value = 43.5

Fuller Index = 175

Matunas Optimum Game Weight = 1468 lbs.

Wootter’s Lethality Index = 306

Arnold Arms Relative Performance Index = 96

Elmer Keith Knockdown Factor = 95 pounds / feet.

Parker Ackley’s Momentum = 66.5

Exterior Ballistics:

Gun / Ammunition : .501 Savage ML

 Bullet          .458, 300, Barnes SpSP .032 457010 (Barnes "Original" 45-70 Semi-Spitzer)

 Bullet weight    : 300 grains or 19.44 Grams

 Muzzle velocity  : 2216 fps

 Crosswind speed  : 10 Mph

 Ballistic Coefficient(s) (G1)= 0.291 (Standard)

 ICAO value =0.286 (International Civil Aviation Organization)

 Table of Various Zero Ranges - Trajectory Path to LOS in inches

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 Range 50 yd.  100 yd.  150 yd.  200 yd.  250 yd.  300 yd.  350 yd.  400 yd. 

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  50 yd. Zero X       -0.5     -3.3     -8.8    -17.4    -29.3    -45.4    -66.2   

 100 yd. Zero +0.2      X       -2.6     -7.9    -16.3    -27.9    -43.8    -64.4  

 150 yd. Zero +1.1     +1.7      X       -4.5    -12.0    -22.7    -37.8    -57.5  

 200 yd. Zero +2.2     +4.0     +3.4      X       -6.4    -16.0    -29.9    -48.6  

 250 yd. Zero +3.5     +6.5     +7.2     +5.1      X       -8.4    -21.0    -38.3  

 300 yd. Zero +4.9     +9.3    +11.4    +10.7   +7.0     X      -11.2    -27.2  

 350 yd. Zero +6.5    +12.5    +16.2   +17.1  +15.0  +9.6      X     -14.3 

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 145 yd.Zero +1.0    +1.5     -0.3     -4.9    -12.5    -23.3    -38.5  -58.3 

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Velocityfps.  2076.6   1941.9   1813.1   1691.4   1575.9   1466.8   1367.6   1278.2  

Energyft.lbs.  2872.4   2511.8   2189.5   1905.6   1654.1   1433.1   1245.8   1088.2   

Deflection      in.     0.4      1.5      3.7      7.0     11.4     16.6     23.4     31.5       

CorrectionMOA/mph  .079    .141    .233    .335    .434    .529    .638    .752      

Time   sec   0.070    0.144    0.224    0.311    0.403    0.501    0.607    0.720   

Interior Ballistics Charts  

The lethality values listed above can be bewildering, and come from a diverse array of sources-- some that have used an equally bewildering basis for their values. Complete discussion of all these values is beyond the scope of this article, but one formula that makes great sense to me compared to most is the "Ed Matunas Optimum Game Weight Formula," as published in Lyman's Reloading Manual, 47th Edition. A representation of those figures appears below, along with relative click adjustments based on 1/4 MOA clicks. The true zero is 175 yards, as you can see. Time of flight is listed as well in 25 yard increments.

The next field test(s) will be precisely this load, along with a Bushnell Elite 3200 4 x 12 x 40mm AO Ballistic Reticle that has 3 minutes between the sighting lines. A 175 yard zero as above will be used. Using the first ballistic line for sighting past 200 yards, the 200 yard -2.1 LOS becomes +3.9 inches @ 200 yards, +1.95 in. @ 225 yards. That keeps us within the range of reality to 275 yards, where LOS is now -4.25 inches.

The alternate approach is a 200 yard zero, giving LOS of +3.51 @ 100 yards. Good to go to 230 yards; -3.14 inches. Shift to line 1 of Ballistic Reticle @ 235 yards = +3.77 inches. At 290 yards = -3.98. Ballistic coefficients commonly improve as velocity slows (see Sierra Bullets multiple BC's for examples) giving us less velocity erosion past 200 yards than typically calculated. Only live fire confirms the veracity of these values.

60 gr. N120 / 300 gr. Barnes Original Spitzer Soft Point / .458-50 Orange MMP sabot nets you about 2300 fps MV. 55 gr N120 nets your approximately 2200 fps.

This will vary by rifle, and ambient shooting conditions, and is only an approximation that must be confirmed by live fire in YOUR rifle: 2300 fps MV 3.2" high @ 100 yards = - 1" @ 200 yards. Est. real-world 200 yard BC (at this velocity) of .252.

Email: randymagic@aol.com

 

© 2005 by Randy Wakeman

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