Iron Content of Rifle Ammo (SS109/M855, M59, M61, M80, M855A1, etc.)

[Icelander]

Originally Posted by DouglasCole

I know you love to indulge in precision, but why not just call it "50% of bullet weight?" It's not wrong, based on your research, and then if you want more (or less, for some reason) iron, you're into specialty ammo so you just charge more.

If it came up in a game right now (and I hadn't found more precise numbers), I would probably do just that, yes.

But it's a neat detail to be able to specify that a given private military contractor is using 20-30 year old Bulgarian M43 rounds and that Occultism and Intelligence Analysis tell the PCs that this is because the iron content is higher in those rounds than in most other available surplus ammo.

I could make up details like that, but it's both easier to keep straight and more fun for me if I am able to find out this sort of information for real. At the very least, I don't want any details I do make up to contradict reality.

For example, knowing the iron content of one or more real bullets to a reasonable degree of precision would be a great help in making up fictional custom round designs, specifically intended for monster hunting (whatever the official stated purpose).

At the moment, I'm mostly stuck on the fact that I have no idea how much of the total bullet weight in typical FMJ rounds represents the jacket and how much of bimetallic copper/steel jackets is composed of the outer copper coating and how much is the mild steel.

I know that there is US legislation where pistol AP ammunition is defined, in part, as bullets where more than 25% of the weight is the jacket. This suggests, but does not confirm, that 25% or less is a reasonable number for typical rounds. It also confirms that any ammo usable in a handgun sold commercially in the US that is available in US stores will have 25% or less of its weight as jacket.

Supporting this is the fact that if 7.62x51mm M80 ball bullets contain 114.5 grains of lead and weigh 147 grains, if the remaining weight is the copper jacket, that makes the jacket about 22% of the projectile weight.

I've found that 7.62x51mm AP steel cores weigh between 58.6-71 grains, which will allow me to know the iron content of P80 or M61 AP ammo pretty well if I can narrow down the relative values of copper and steel in bimetallic jackets.

That would be nice, as in real life, CBC Defense in Brazil makes a 7.62x51mm AP round which seems to have a fairly long 71 grain steel core and looks promising as the ammo that would have been most easily acquired for Brazilian military hunters. Depending on the weight and steel content of the bimetallic jacket, such a round could be as much as 55-60% iron, even without a custom monster-hunting version.*

I also have to determine how much total iron content is plausible for a round designed from the ground up as a monster hunting round. Granted, pure iron is soft enough to engage rifling, but in my campaign, I'll have the fancy cold-forged pure iron rifle ammo that johndallman and Rupert advised on designed by RUAG in Switzerland and sold only to Vatican-backed monster hunters or those with relationships based on mutual trust with them. Those making monster hunting rifle ammo with more traditional and less expensive methods will need a jacket similar to normal rifle ammo and probably less pure iron and more very mild steel.

So manufacturers like POF in Pakistan, Fiocchi in Italy, CBC Defense in Brazil and others in other places that have some supernaturally-aware contacts will make rounds that are essentially inspired by existing mild steel rounds, but simply use more iron in preference to other materials where possible without major cost or performance effects.

*Which I'll have introduced around 2012-2013, but not necessarily available to all the smaller Brazilian police teams that encounter supernatural threats without necessarily knowing about the larger context or having any contacts with the secret anti-supernatural faction within Brazilian intelligence, military and security establishment.