22 July 2017

Statting The M855A1

M855 from a 14.5" M4 barrel is 4d+2 pi.

Despite the steel penetrator, it's not considered armor piercing.

This is mostly because the 600m distance to punch the DR 4 of a steel pot is well within the 800 yard 1/2D distance of the 5d pi from the 20" M16A2 barrel and the 750 yard 1/2D distance for the M4.

The minimum damage from both an M4 and M16A2 penetrate that helmet.

The 1/2D for M193 from an M16A1 is 500 yards, the minimum damage from 5d pi won't penetrate now.

With me so far?

From the physical description of the M855A1 bullet, it conforms to how High Tech describes TL6 Armor-Piercing (AP) ammo.  That would change the damage to 4d+2(2) pi-.  The problem with this is M855A1 appears to perform no better against armor or barriers than M855 and is comparable to M80 ball in tissue.  pi- would be worse soft tissue performance than before when the reports are saying it's better.

7.62x51mm NATO M80 ball is 7d pi.

M855A1 fired from an M4 is reportedly doing comparable soft tissue damage to M80.

OK.  Giving M855A1 hollow-point status brings the damage to 4d+2(0.5) pi+.

7d pi does 7-42 points of damage.  24 average.

4d+2 pi+ does 9-39 points.  24 average.

That is comparable.

The niggling problem now is the (0.5) armor divisor for going hollow-point.  By all accounts, M855A1 doesn't behave differently than M855 against barriers or armor.  (0.5) would give unarmored targets DR1 and would double the DR of armored targets.

Thus 4d+2(0.5) pi+ shouldn't penetrate the, now, DR 8 of a steel pot with minimum damage.  Yet, it does.

The way the round appears to behave is 4d+2 pi+.  Not sure what generic label to apply to it here though or what it should do to the cost per shot, especially since it's shaping up to be not a lot more expensive than M855.

This going to matter because they're applying this technology to 7.62 as well in the M80A1 round.

One way to explain it can come from M855 being the US version of FN's SS109, which was developed in the 1970's, and is thus a TL7 round, 1980 being the cut-year between TL7 and TL8.  Thus M855A1 is a TL8 round.

There's only three TL8 kinetic energy bullet types listed in High Tech and they're all depleted uranium armor piercing rounds.

I think I shall call it:

Enhanced Performance Ball (EPB) (TL8)

This ammo is made from a hardened steel tip with a lighter metal core and is designed to cause more damage to soft tissues via tumbling and fragmentation, without sacrificing penetration against armor or barriers.

Change damage type: pi- becomes pi, pi becomes pi+, and pi+ becomes pi++ (no effect on pi++).  Multiply CPS by 1.2.  LC2.


  1. Aha, I saw this, wanted to use it, then forgot and closed the saved tab. Just dug back for it, since it solves part of my issue with trying to make bullets that hold up against the near future. Is this technology compatible with AP ammunition, do you think?

    1. I am thinking that it is not compatible with the AP modifier because the bullet is intended to come apart post penetration. An AP round retains integrity.

      But I expect there's a TL9 round that will be both AP and expanding... I've used stats like that for the 4mm Gauss rifle in traveller.


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