Home Forums Hunting & Shooting Ask The Gunwriters Old bullets = more fragile bullets??

I have seen bullets corroded before but it was because of atmospheric exposure to acids, ammonia can do the same. This was discovered in the Civil war when munitions were stored in horse barns, the ammonia went to work on both powder and bullets destroying them. I have not seen this happen from age hardening to the point you could observe it. Used to shoot a lot of surplus ammo some probably even from WWI and as long as the primers were not corrosive there were no issues.

I have some issues with the Ballistic Reports like when they say so and so bullet is good to 200 kilos, does that mean if the animal is 201 kilos the bullet will bounce off? There are many other demonstrative statements in the reports that just don't hold water. Even though the guy has lots of experience his rational sounds like it is true because I say it is so.

Gnoahh hit it on the head. Exactly right.

You did right by them, and it paid off, I'm sure. Great story all the way around.

I took some Remington 30-06 220 grain Core-Lokts made in the 1970's on a Moose hunt in 2009 . I shot a broadside Moose twice and didn't recover either bullet. I don't think the bullets were compromised much if at all

Thank you sir. We truly enjoyed having them live with us for almost two years. Both great young folks. Both have servant hearts. Proud to have them in our lives.

I, also, find this theory surprising, and not a match to my own experience.

Annealing is a "softening"/stress relieving process, not hardening.
The guy at ballisticstudies.com has issues with confusing his opinions with facts.

to add: copper does harden with age as do other metallic materials but "natural annealing" is not happening.

As a metallurgist, at least in a former life, I guess I've become used to some strange sorts of ideas being floated around about how metals actually behave. Ideas like metals getting softer, or harder, as they get old are more of less akin to that great fad for cryogenic quenching which was around a few years back.

Sometimes there's a grain of truth, or more often some half-understood fact which then gets generalised beyond its actual applicability. People will make a comment about, say, "stainless" for example while ignoring the fact that there are several distinct families of stainless steel, with widely different properties.

Here's what I'd say about jacketed bullets getting softer over time:

Bullet jackets are mostly of a composition somewhere between copper and cartridge brass - ie copper with less than about 30% zinc. At this composition the zinc is completely dissolved in the copper, and the solution is stable at room temperature. What this means is that you can't precipitate the zinc out of solution so you don't get age hardening, and the alloy can't be heat treated to increase hardness. The only way to increase hardness is by cold-working, in other words, deformation such as rolling, drawing etc. What this actually does is create dislocations in the crystal lattice that makes up the metal, and the more of these there are the harder it is for atoms to slide over each other, so what you see on the macro level is that the metal becomes harder.

You can reverse this effect by annealing, which means heating the metal to a high enough temperature for the atoms to move around freely enough to reorganise themselves, and for long enough that they re-order themselves to eliminate the dislocations in the crystal lattice. Now in the case of these brasses this doesn't happen at room temperature, even over protracted time periods. You need to heat it up, and indeed the temperature required is hot enough that a lead core would melt.

Lead alloys used in bullet cores are more or less pure lead in most cases, and very soft. It'd be hard to see how they'd get much softer without you heating them up enough to get runny.

Of course, it is possible to make age-hardening lead alloys, and they aren't uncommon in bullets, but not usually for jacketed.

Age hardening is a bit of a misnomer though. The more accurate name is precipitation hardening. What you need is an alloy that is not a stable solid solution (ie not your alpha brass or copper). You need an alloy where you can dissolve something in the microstructure (sorry to the engineers, but I'm trying to keep this simple) and, with controlled time and temperature, cause it to precipitate out in a controlled way. The ideal scenario is that you get a fine, well distributed precipitate in the microstructure. This serves to "pin" or obstruct atoms from sliding over one another in much the same way as cold-working does. In a well-considered precipitation-hardening alloy this microstructure is stable at room or working temperature and so maintains its properties. It is possible to "over age" though, usually as a result of keeping it at a higher temperature for too long, upon which the precipitate particles can coalesce, becoming fewer and coarser and reducing their ability to impede slip, and so reducing the hardness. This is perhaps the grain of truth here, but I do not readily see a case for it with jacketed bullets, as they are not usually made from alloys which exhibit this behaviour.

That's the short version ;-)

thanks Dan, your explanation pretty much ends the speculation for me.