Requirements for Replacement of Currently Issued 5.56 M-855 and 7.62 M-80.

[stanc]

...back to the requirements list. Are there any additional comments on the threshold and objective statements for item #1? I plan to tweak again in the next day or so.

So, item 1 should have:
•Threshold: At least equal the vertex and wind drift seen by the 7.62X51 NATO M80 at 1000 metres when using a 20-inch barrel.
•Objective: Reduce the vertex height by at least 10% and the wind drift by at least 20% compared to the M80.

I have no comments. Out of curiosity, I ran ballistics tables for both calibers, to 1000 yards (~900 meters), assuming 20" barrels, and using BC of the Barnes 6.5mm solid.

7.62 NATO vs 6.5 NATO

Range - yards _0_ _100 _200 _300 _400 _500 _600 _700 _800 _900 1000

7.62mm 147gr @ 2700fps BC=0.418
Velocity - fps 2700 2488 2285 2094 1912 1740 1579 1435 1306 1198 1111
Energy - ft-lb 2379 2019 1705 1430 1193 _988 _814 _672 _556 _468 _403
Path - inches -1.5 43.3 82.5 114.9 139.5 154.4 157.9 147.4 120.0 72.1 0.0
Drift - inches _0.0 _0.4 _1.6 __3.7 __6.9 _11.3 _17.0 _24.2 _33.1 43.6 55.9

6.5mm 110gr @ 2650fps BC=0.450
Velocity - fps 2650 2454 2268 2090 1921 1760 1609 1472 1347 1239 1150
Energy - ft-lb 1715 1471 1256 1067 _901 _757 _632 _529 _443 _375 _323
Path - inches -1.5 42.5 80.6 112.0 135.4 149.4 152.2 141.4 114.6 68.6 0.0
Drift - inches _0.0 _0.4 _1.5 __3.5 __6.5 _10.6 _15.9 _22.6 _30.8 40.5 51.9

I must say, the results surprised me.

So, it appears possible to match 7.62 NATO trajectory and wind drift. Next step: Terminal effects.