Discussion about 5.56x45 and 5.45x39 bullets internal components

I’ve been documenting myself for a while about the bullet itself and now I’m stuck with this question regarding its components. A bullet can have a metal jacket, a core and a thin metal layer that separates the core from the jacket. Thus, we can have three types of bullets: a one-component bullet (only a solid core), a two-component bullet (a solid core inside a metal jacket that can or cannot feature a filler situated in its forward or rear portion) and three-component bullet (a solid core inside a metal jacket alongside a thin metal layer that separates them).

My question is as follows: is a 5.56 M855/M855A1 a three-component bullet since inside the metal jacket there’s only the steel penetrator and the lead slug (for M855) / steel core that protrudes outside the jacket and a copper plug (for M855A1)?

And I also want to question you guys, a 7.62x39 PS (M43) is definitely a three-component bullet (I’ve seen it with my own eyes), but is 5.45 PS (7N6) (a three-component bullet as well (which I think it is)?

Plus, general speaking, not to be confused about those terms, is “penetrator” a synonym for “core” (as it is in a steel core bullet) and “slug” a synonym for “filler”?

7943342_orig

cross_section

7.62x39 PS (M43) bullet:
7_62x39_PS_2

5.45x39 PS (7N6) bullet:
5_45x39_PS_2

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I di not know id his is any help, but here is one description from 2012 of the difference in the M855 & M855A1:

Badger - is that “Comparison of Changes” a single-sheet flyer, or is it part of a larger document? If the latter, do you have a click-on reference to bring it up?

John Moss

MarchHatchet,
your association of part counts with the bullets you mention is correct. But this way of assigning bullets to classes is unusual. Normally other criteria are used, in particular the intended purpose.
For example, 7.62 mm PS and 5.45 mm 7N6 have steel cores, but for reducing the amount of lead consumption, not enhanced penetration. The same applied to the U.S. 7.62 mm NATO M59 (4 parts), which was replaced by the lead core M80 (2 parts). All are intended for use against unprotected and lightly protected targets.
On the other hand, you have bullets with a hardened steel or even tungsten core to penetrate arrmour. Some designs are 3 part, but others, similar to the M59, have separate base and nose fillers, adding to the number of parts.
The M855A1 bullet in design and purpose is very different from the M855. It is not just a minor change, as the A1 postfix suggests. The totally new M855A1 is in line with a trend in the U.S. military to adopt bullets designed to deform and/or fragment at relatively low speeds in human tissue (Mk 262, current M118, Mk 316, Mk 318). The U.S. interpretation of the Law of Armed Conflict (see DOD Law Of War Manual) considers easily deforming bullets as legal.
The M855 (FN design SS109) was primarily designed to penetrate Soviet era body armour at considerable range and stay intact in the process, in line with the conventional interpretation of international law.

Slug is the name used in U.S. Ordnace drawings for the lead core of a bullet. And filler is used for small lead parts to fill voids. Outside this, a slug is usually the name for a projectile fired from a shotgun. (And slug is a unit of mass in ballistics!)
Regarding solid (jacketless) designs, penetrators versus hard cores and the like, there is no generally used terminology as far as I know. In Germany we have the confusing situation that “Doppelkern” described a hunting bullet design made by RWS for decades, but also is the military term for our lead core/steel penetrator SS109 clone.
For the relatively new solid bullets, there is no standardized terminology yet, in particular not for the “saddles” and “driving bands” on the outside shape for reducing friction and modifying air drag.

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John, it is from a presentation we had on ammunition aquisition at one of our club meetings, (I am the club photog), and I grabbed shots of a couple of the more interesting slides.
It covered comventional small arms, close combat systems, towed artillery, anti-mine/iED/force protection, precision and non-standard munitions, among others.

Here are the other three slides in the 855/855A1 section:



I believe that this may be the source document:

https://www.dau.edu/cop/ammo/DAU%20Sponsored%20Documents/Public%20Release%20EPR%20Apr12.pdf#search=PM%20MAS

Seems like, but the presentation, (well over an hour long), covered so much more, like this:

Thanks guys. I will print out the referenced paper, as well as this thread. Don’t collect 5.56, but like having good material like this in my library, which me being an old goat, is a print library, not computer stored information.

john M.

JPeelen,
I think I get this, my mistake or my confusion if I can call it like that. I was mostly looking at the soviet/russian 7.62x39 PS which had that thin lead layer (7.62x54R as well), thus I considered it as a model for the three-components bullets, going from the exterior to the interior of the bullet, bimetal (jacket) - lead (layer) - steel (core). I looked at this as numbers of a bullet “layers” and not necessarily as “components”, this being my mistake. The book “Construction of Cartridges” by Mikhail Grinberg, at the section “Firing accuracy and firing dispersion” where he talked about the eccentricity of the gravity center of a multicomponent bullet, influenced me into considering bullets like I did above, with one, two or three components, which I should’ve considered from the very beginning as layers, not components.

Different cross-sections proved me that different AP bullets have those three layers as well. Modern ball bullets, layers-speaking, have only two. Solid bullets and frangible have only one layer.
When we speak about components, there’s a different talk. As you’ve mentioned, there can be bullets with even four components (and I’m not referring here to spotter bullets as an example). Those bullets can have cores, penetrators, slugs, fillers, jackets, etc. (Terminology, I get it). And I haven’t even yet included the combinations like an API-T in which you know there are other fancier components, different compositions.

What I want you to confirm to me is that is it correct this view I considered, the one regarding layers from outside to inside of a bullet?
The components are different and, as you’ve told me, I have to take into consideration its purpose and its country of origin (the talk about M855 and M855A1). That’s why there are many types of bullets which can have different combinations of components. A full core made of a steel penetrator and a lead slug as an example.

I beg to differ from your view. In my view 2-layer AP bullets are not necessarily the modern way, but the U.S. way of designing them. If you look at the drawings in Hackley/Woodin/Scranton Vol. 1, even in early 20th century, the U.S. AP designs were of the 2-layer type. Partly made possible due to using relatively thick gilding jackets.
On the other hand, modern German AP bullets from the 21st century (5.56 mm DM31, 7.62 mm DM151, 7.62x67 DM131, for example) are of 3-layer design. The hard core sits in a sleeve, closed at the rear like a cup, made of aluminium alloy or lead in the case of DM131.
The modern Russian 7.62 mm 7N14 is still different, having a penetrator (relatively larger than in M855) sitting in front of a lead core which fills the entire rear of the bullet.
The opinion that many parts add up to large weight tolerances and favour possible imbalance is of course basically true. But you have to consider that U.S. military tolerances, for example as defined for the NATO M59 bullet (Ordnance drawing in the Royal Armouries Leeds), seen through Continental European eyes, are a little on the lax side.
In my view the main problem in AP bullet design is keeping the core from shattering, not bullet dispersion. Add barrel life to this, to which 2-layer designs pose a greater challenge, because they are significantly harder in every sense.

In short: I do not think that 2-layer designs are more modern than 3-layer designs.

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And one last question regarding to what you’ve said about the barrel life. Does that thin lead layer which encase the core at the interior has a role into reducing friction between the core and the barrel lands, thus improving barrel life? Obviously when a hardened core material is used, i.e. hardened steel, AP bullets core like tungsten, etc.

Yes. We always deal with tolerances in bullet as well as bore diameter. In a “tight” situation, the very hard core can practically not deform. The barrel has to “give in”, which creates sharp stress peaks. Note that we are still in the elastic zone of deformation. After the bullet passed, the barrel springs back to its original shape.
If some (in comparison) easily deformable component like lead or aluminium alloy is present, it will deform just the right degree for each bullet/barrel pair. The peak stresses on the barrel are lower and the danger that pieces break from the lands is less.

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