Zinc bullets, why harder on bore than copper?

[Chicken Thief]

Soft iron and sintered iron driving bands for artillery projectiles were introduced at least as long ago as WW2 and are used by many counties today. At one time Norma produced steel jacketed hunting bullets and of course almost all military 7.62x39 mm ammo has steel jackets. If steel doesn't wear them out why should zinc?

The trick is copper plating to reduce friction.

And i'll bet you that a barrel wont survive 5000+ of them steel clad bullets with presition to spare.

But why not just swage the zink? Is there a need for lube?

[Chicken Thief]

Zink Oxide ZnO has a hardness of 4.5 Moh~72 Rockwell

http://en.wikipedia.org/wiki/Zinc_oxide
http://www.cidraprecisionservices.co...onversion.html

Compare that to a rifle barrel of something around 40'ish Rockwell.

Then again copper oxide CuO has a Moh hardness of 3½-4.

http://www.galleries.com/Cuprite

Alu oxide Al2O3 is "pure" sapphire/ruby and a fine abrasive.

http://en.wikipedia.org/wiki/Aluminium_oxide

So lets just shoot and have fun.

[Chicken Thief]

Just had a


Copper wears of and fouls a barrel, so does most other things.
How to clean Zink?

[Thompsoncustom]

How to clean Zinc

sodium borate (borax) works as a flux for zinc.

[jabilli]

Lots of great answers/info! Thanks guys

The other day I got a small amount of zinc and a torch, heated up my mold (steel .223) and had about enough molten Zinc to fill one cavity and still have a sprue. I noticed immediately that Zinc doesn't seem to be as fluid as lead (I'm guessing this can be remedied by hotter temperatures?) It was reluctant to move...then suddenly and very quickly moved when it finally did. >< After pouring, it solidified faster than I would have liked: I found the sprue wouldn't break... (at least with the amount of force I was willing to place on it.) I chose to partly disassemble the mold and Dremel the bullet out. It formed pretty well, especially considering it was the first cast (usually the first few of my lead boolits turn out kinda, "Meh.") and how short the amount of time it was in the mold before solidifying.

It seems a few places talk about shooting Zinc/Aluminum alloys...My question...Why Aluminum?? What does it do/give you?

I'll share what I have found out about about Zinc/Aluminum alloys It seems that Zamak is the trademarked name for a family of alloys... Zamak 3 is the alloy of theirs that is a base for all of their other alloys. Zamak 3 is 96% Zinc, 4% Aluminum. The alloys are known for being the material many components (Including slides, receivers, and bolts) are made of in Hi-Point's firearms.

From what I read, to mix in Aluminum in molten Zinc, people are simply stirring it in the Zinc and it dissolves (Amazing really, considering the melting temp of Aluminum is something like 1200 and the zinc is much lower, something like 800ish I think)...I read this to be done with solid objects like rods...Anyone know if other forms of Aluminum can be mixed in?? (Powder/molten) I read somewhere it can be fluxed with Aspirin (salicylic acid)...I'd double check on that, sounds potentially harmful.

I do know that casting with pure Aluminum causes shrinkage...Objects cast come out something like 2% smaller after they cool. I wonder if this has any effect on Zinc/Aluminum bullets... Anyone know ?

@ Thompsoncustom- Wow look at that, looks like a piece of jewelry. :-p Have you gathered info (Loads/performance data/ Accuracy/notes about wear/ect.) about those bullets by chance? How do you make them? (As you can read above, I ran into some trouble getting the sprue to break.) Related to my shrinkage question above- What size do they drop out at?

[Thompsoncustom]

LOL you got to be quick and hit that thing as soon as you pour the bullet pretty much. I've cast oh maybe 100 but never got around to testing them for accuracy. I used Quickload to help in developing loads for the light bullets. I don't think they wear any more than copper bullets but they do take a little more force to size than lead ones.

I noticed immediately that Zinc doesn't seem to be as fluid as lead

When I start casting pure zinc bullets I noticed the same thing and that's the reason I add aluminum to mine seems to be like adding tin to lead bullets. A pop or beer can works well as they are really thin and dissolve easy into the zinc not sure on the temp it takes but around 800 sounds right maybe lower. Ya it's weird to think about but your not melting the alum your dissolving it like salt in water.

I do know that casting with pure Aluminum causes shrinkage...Objects cast come out something like 2% smaller after they cool. I wonder if this has any effect on Zinc/Aluminum bullets... Anyone know ?

I don't really remember but I don't think they cast smaller because I sized them to .3565 and it was shaving them.

My latest project with zinc is going to be trying to make a hard nosed bullet with the front half being zinc/alum/and maybe some copper and the back half being lead. Tho the cheap lee mold I got for the project needs a lot of work I already removed the crimp groove but need to make the nose longer and shave the top 1/4 of the mold so I have no idea if this is going to fail from the start or not but lee molds are cheap so I figured why not.

[jabilli]

Very cool, thanks for the info.

Interesting idea- Best of luck, stay safe. I spent a minute or two trying to think of a way to make a bullet with a lead rear and a Zinc front, and have each one be almost exactly the same...I'm curious if molten Lead would adhere to Zinc...If so, you could cast out a bunch of noses (cut to same size/shape via a sprue) , then take the noses and place them in a mold point-down where you could cast the rear of each bullet on top of each nose. Sounds unlikely to work.

Probably a more likely thing to work would be to cut a thin lead disc, then sandwich it between the base of a bullet and an attached gas check.... Wonder if that would work. OR...if having a lead base isn't an issue, a gas check made O-lead?

[Thompsoncustom]

those sound like some great ways to do it but I was thinking something much simpler. I am planing on cutting a dipper to only hold the amount of zinc I want per bullet and then filling the rest with lead but I'm not sure how they will adhere as the zinc will have to start to set up a little but should be hot enough to keep the lead molten for a bit. Because if you mix the two molten the heavier one will sink. Doesn't have to look pretty just has to work.

[williamwaco]

Not sure who told you that zinc would wear a barrel faster than copper but I am with you and think that is incorrect. There were boolits made that incorporated zinc "washers" essentially attached to the base of the boolit. These were called Pro-Tex:

http://castboolits.gunloads.com/show...c-driving-band


That's my take anyway.

Longbow

Found this last night:



I see the molds to cast these occasionally at gun shows.

.

[MikeS]

Why would you want to remove crimp grooves, or lube grooves? I would think that even if you're not going to use lube (it's not really needed with zinc boolits) that you would be better off leaving them. First off it would lower the amount of zinc in contact with the bore and so would lower the friction of the boolit going down the bore, and also, just like the solid copper (or is it brass?) bullets have grooves in them, that leaving the grooves in a zinc boolit would give it the same advantages as the copper bullets. I forget all the reasons they put the grooves in the copper boolits, but I'm sure the zinc boolits would have the same reasons for having them. And a crimping groove? no reason to remove it, unless you feel you will NEVER crimp the boolit in place. Even jacketed bullets that are designed for cartridges where the bullets would be crimped in place have crimping grooves, only they don't call them that, they call them a cannalure (sp?).

[jabilli]

Williamwako-
Cool find- thanks!

[geargnasher]

Zamak "cores" when it shrinks, as do most zinc alloys and pure zinc. Someone here built a vibrating mould rest with an electric razor to assist fillout and reduce coring. Traditional sprue plates are insufficient to cut zinc without tearing them up in short order, special moulds with something like a sprue-hole-sized gas check shank and integrated sprue well would work, the sprues can be cut off after casting but would make cherry-cut moulds really difficult to make considering the weak point in the cherry.

As far as bore wear goes, anybody consider what is in gilding metal alloy?

Gear

[BAGTIC]

At least four countries are already using steel bullet. France is one and Nammo which supplies ammunition to Sweden, Norway, and Finlands has developed steel bullets which have been accepted by the military.

Here is a link to a 1951 paper related to the development of soft iron driving bands for the high performance 3/70 naval AA gun. It shows that the hardness and friction of the iron bands is no higher than for copper. If 1951 metallurgists could manage it I think modern ones could do at least as well. Now none of this will help those who want to make their own at home but it shows that just because something has never been done before or because we have never heard of it is not cause to say "It can't be done". www.dtic.mil/dtic/tr/fulltext/u2/499469.pdf

[jabilli]

Interesting read!
First thing that came to mind: Who were the poor fellas that had to go find and retrieve the projectiles? lol "The average ranges wore 14098 yards and 14036 yards, respectively."

I've found something in particular this article mentions to be thought provoking...Before I jump on it excitedly only to feel like an idiot later, I'll spend a bit of time reading into it first. :-p

The document seems to me to have been a request for more testing (send money please.)...I wonder how it was received?

IMO, If I were charged with the task of arming a naval ship with an AA gun- given the choice between wearing the barrel to be more accurate, or choosing projectile materials that conserve the bore, no doubt, give me the barrel wrecker. A nicely treated bore won't be of any use at the bottom of the sea.

[BAGTIC]

1) Zinc bullets don't need lubricating.
2) Grooves in the bullet degrade the ballistic coefficient.
3) Grooves result in a longer bullet which reduces case capacity.

[BAGTIC]

This particular gun was notably unsuccessful due to problems with the mounting. After 12 years the Navy gave up partly because by that time the age of the SAM was fast approaching.

What I found interesting was the observation about where the greatest bullet (driving band) erosion occured. It was not atop the lands or in the bottom of the grooves. It was against the leading edge side. One the projectile had been engraved there would be little wear or friction except on the back side of the rifling where most of the stress occured. This points out the nature of rifling or any other screw as being an inclined plane, like a ramp, and most of the wear occurs on the load bearing side.

BTW the barrel was chrome plated and water cooled. Normals barrel life was 2,050 rounds when firing the ultimately adopted load (45,000 psi ) of 11.2 pounds of powder propelling a 15 pound projectile at 3,400 fps. ROF for a twin mount was 90-100 rpm. This compared with the older twin 3/50 3 inch gun which fired a 13 pound projectile ahead of 4 pounds of powder (34,000 psi)at 2,700 fps at 45-50 rpm with the same barrel life of 2,050 rounds. It seems that despite much higher performane barrel life did not suffer from the iron bands.

[jabilli]

Zamak "cores" when it shrinks, as do most zinc alloys and pure zinc. Someone here built a vibrating mould rest with an electric razor to assist fillout and reduce coring. Traditional sprue plates are insufficient to cut zinc without tearing them up in short order, special moulds with something like a sprue-hole-sized gas check shank and integrated sprue well would work, the sprues can be cut off after casting but would make cherry-cut moulds really difficult to make considering the weak point in the cherry.

As far as bore wear goes, anybody consider what is in gilding metal alloy?

Gear

I'm thinking I will try to use higher operating temperatures which allow me a little bit more time to cut the sprue while semi-molten. Afterward I'd just buff out any lines. If not- it seems cutting might be the way to go- Someone else in the forums claims this is his standard practice- I'd like to throw out his name but I forget who it is and searching for it just now did not bring up his post.

1) Zinc bullets don't need lubricating.
2) Grooves in the bullet degrade the ballistic coefficient.
3) Grooves result in a longer bullet which reduces case capacity.

Personally I'd (at least for now) rather not alter my mold, given a choice.
I'm quite confused as to the third statement: "Grooves result in a longer bullet"... hrm? I do understand that under pressure from being fired a bullet with grooves lose a bit of length due to being squished from the pressure/obturation (...Someone verify this please?) but I don't see how having grooves will make a bullet longer (thus causing higher pressures when given a static OAL)? Am I missing/misunderstanding something?

I have read that lubing cast zinc boolits isn't neccesary from another thread or two, one even citing an old magazine article making this claim-
Not for the purpose of "HEY I DON'T BELIEVE YOU/THEM" but, are we sure this is so? Thinking out loud for anyone that's wondered this:

Questioning whether or not lubing is necessary, we might first ask- What does lube do?
1. Help fill in gaps where air may try to pass through (even .001 can let a relatively large amount of gas through under pressure) thus minimizing gas cutting, thus reducing bullet deformation and leading.
2. Helps reduce leading via lubricating the contact point between the bullet and the bore.

Considering this, why is lube not needed for Zinc?

This got me wondering, "Hey...Why don't we lube jacketed ammo?"
A quick google brought me here: http://www.leverguns.com/articles/ta...llet_lubes.htm Interesting to have a gander at.

IF this is so, I'd imagine the main reason for why it is not commonplace for jacketed ammo to be lubed is that it might be much harder/more expensive to make swaging equipment that makes jacketed projectiles with lube grooves.

[captaint]

All this discussion is great, BUT - why doesn't somebody just go pour up some Zinkers, load & shoot them and tell us all how they worked ?? After all, that's what we want to know anyhow !!
So, jabilli, go make some and get back to us, please !! Mike

[I'll Make Mine]

I'm quite confused as to the third statement: "Grooves result in a longer bullet"... hrm?

I think that was meant as something along these lines: "A lube groove boolit will be longer than the same weight without grooves, hence potentially reducing case capacity if it has to be deep-seated to avoid interference with the rifling when the round is chambered."

[jabilli]

All this discussion is great, BUT - why doesn't somebody just go pour up some Zinkers, load & shoot them and tell us all how they worked ?? After all, that's what we want to know anyhow !!
So, jabilli, go make some and get back to us, please !! Mike

You're right absolutely right. My apologies- I'm getting off my keester and getting it done. Thanks Mike