A digression about armor penetration

Over on the boards at Juhlin, I've been involved in a discussion of armor penetration, since I was encountering some odd effects when trying to emulate modern body armor. I figured I'd repost some of the information here.

The problem I encountered is that on the canonical weapons calculations from Fire, Fusion & Steel, there are two places on the charts where it's possible for a weapon with more muzzle energy to have less penetration capability. The first is where the chart goes from 1-Nil to 2-Nil, and the second when it goes from 2-3-Nil to 2-4-6. As such, I proposed (and am proposing) a revised armor penetration stat calculation:
Up to 600 joules, Pen remains Nil
From 600-2000 joules, Pen changes from 1-Nil to 2-Nil
From 2000-3000 joules, Pen changes from 2-Nil to 2-4-Nil
From 3000-5000 joules, Pen changes from 2-3-Nil to 2-4-6
From 5000-10000 joules, Pen changes from 2-4-6 to 2-3-4
From 10000-20000 joules, Pen changes from 2-3-4 to 2-2-3
Over 20000 joules, Pen changes from 2-2-3 to 1-2-3

Black powder weapons move up one row on the table (e.g. a black powder weapon with 7000 joules of muzzle energy would use the 3000-5000 stat, either 2-3-Nil or 2-4-6).

For the T-Gewehr, this would mean it would have Pen 2-2-3 instead of the listed 2-3-4; against vehicles, it would go from 4/2/2 to 4/4/2, making it effective up to long range against most early tanks.

Any future small arms mentioned will list both sets of Pen stats so that either one can be selected by someone using the equipment in their game.

Edit: The original version of this post accidentally used the energy levels for black powder weapons instead of modern firearms. That has been corrected.