aluminum jackets

[MeestaSparkle]

Would someone care to tell me why aluminum jackets are not more popular, or point me in the direction of information on the topic? Aluminum seems like it would be easier on barrels, and is definately cheaper; it does have a lower melting point though. I did some googling but did not find a whole lot of info on the subject.

Thanks!

[stocker]

There are a couple of issues that may or may not apply to aluminum used for bullet jackets. The first is that aluminum is what I would call a "sticky" metal. It drags hard against any surface which is harder than the aluminum. Ever drag an aluminum boat over rocks and feel it grab? It does and it galls and abrades at the same time. Despite being softer than steel I think aluminum can be quite abrasive and have seen some sanding papers made from aluminum oxide and I say up front I don't know if there is any comparison with that and straight aluminum. There is probaly a metallurgist on this forum that can enlighten us both. I question the use of pop can aluminum for gas checks and wonder why, if it is indeed suitable for that purpose, they are not produced commercially. Good question and I hope some one can give us the real skinny here.

[floodgate]

stocker:

"Despite being softer than steel I think aluminum can be quite abrasive and have seen some sanding papers made from aluminum oxide and I say up front I don't know if there is any comparison with that and straight aluminum. There is probaly a metallurgist on this forum that can enlighten us both."

I'm NOT a metallurgist, but I have some familiarity with this topic. Yes, on exposure to air (oxygen), aluminum forms a film of aluminum oxide (which is the base molecule in sapphire and other hard gems, often used as abrasives). But more to the point, in the absence of some very specific lubricants, aluminum will bond to steel under pressure and rapid relative movement, the process is known colloquially as "galling". You'll encounter it trying to turn the sprue-plate screws from Lee moulds. You could try it, but I think it would make a mess. BUt then,"Practice beats theory, every time!."

floodgate

[felix]

Stocker, you already said it without realizing it. Aluminum cannot "draw" correctly to make gas checks with it. Larry the Gator has been toiling with this idea for some time, and has been in the market to find some cheap aluminum alloy that will draw and not crack using the current equipment that works fine with copper alloys. ... felix

[stocker]

Thanks felix: I'll continue to avoid the concept until it's proven by some one else.

[Ricochet]

How's Winchester managed it with their Silvertip pistol bullets? That would appear to be an aluminum jacket, like the aluminum tip jackets on Silvertip rifle bullets.

[pumpguy]

I thought Winchesters bullets were some type of nickle plated metal. Shows what I know and why I cast!!!!!!!

[felix]

Yeah, good question. Prolly not aluminum? Some secret aluminum alloy? Maybe a nickel-copper alloy which has been proven over the last 100 years. That stuff draws very well, but would not be cheaper than zinc-copper in plate form, I bet. The better "air conditioners", using salt water sumps, use nickel-copper exchangers, so it must be available in some kind of plate form. I had my water system (geothermal) units made with it so I could use my swimming pool as the sump. ... felix

[45 2.1]

Stocker, you already said it without realizing it. Aluminum cannot "draw" correctly to make gas checks with it. Larry the Gator has been toiling with this idea for some time, and has been in the market to find some cheap aluminum alloy that will draw and not crack using the current equipment that works fine with copper alloys. ... felix

The aluminum plates that printers use work fine if the right tooling is used. Castalot made a set of gas check forming dies that i've seen and used. They work fine though the check needs to be crimped on (not in a lubesizer). The plate thickness was 0.075" which could be thicker and probably work better.

The freecheck discs made from soda cans need to be lubricated on both sides or they will tear while being formed also. Probable solution would be a dry lubricant to facilitate forming.

[S.R.Custom]

How's Winchester managed it with their Silvertip pistol bullets? That would appear to be an aluminum jacket, like the aluminum tip jackets on Silvertip rifle bullets.

Some of Winchester's silver tip pistol bullets are nickel (plated?), usually in the magnum calibers. You can tell them-- they are the shiny ones. Those are pretty good bullets.

But... The duller colored stuff is indeed aluminum, and I know for a fact they used it on the .380 bullets. I once put about 100 rounds of Winchester Silver tip through a Walther PPK, and the stuff fouled the bore like you've never seen. It took four stainless steel brushes to get all that crap out --the only kind of brush that would touch the stuff-- and the vigorous use of the steel brush didn't do the bore any favors, either.

[floodgate]

Felix:

I once had a chance to visit a plant making 37mm shell cases in 4" to 8" lengths for military pyrotechnics (we used them to dispense silver iodide smoke for cloud seeding); they used an "impact extrusion" process, whereby a ram slammed into a wafer of heated but still solid aluminum and the sidewalls jetted up through a surrounding die around the ram mandrel. I have no doubt gas checks could be formed the same way - but the tooling process would be horrendously costly, and I'm sure a special alloy is needed to work properly. But an aluminum GC would still have the galling problem, I would think.

Floodgate

[felix]

We have to get around the galling problem using everybody's current molds, dies and guns. There is no doubt there is an alloy of aluminum that we can use. Has it already been formulated? Who knows. ... felix

[NuJudge]

I saw a bunch of Winchester's aluminum-jacketed pistol bullets pulled right after they came out, and they had a lubricant-filled ring around them.

CDD

[felix]

Well, I guess that the lube ring is there because Olin has not yet got the right alloy, but one that works half-way anyway. Olin is prolly the leader in metal alloys outside of Germany (chemistry in general for those Germans). ... felix

[jh45gun]

Would someone care to tell me why aluminum jackets are not more popular, or point me in the direction of information on the topic? Aluminum seems like it would be easier on barrels, and is definately cheaper; it does have a lower melting point though. I did some googling but did not find a whole lot of info on the subject.

Thanks!

Lead is easier yet

[woodman51jfk]

I'm with SuperMag on those SilverTips....I ran a couple of boxes thru my Dan Wesson .357, and never saw such a bunch of crud that acted like it was friction welded to the bore!

[beagle]

Looking at the wear factor and this is cases and not bullets. In VN we used a bunch of 40mm belted ammo on our Cobras. This ammo had lacquer on the annodixed aluminum cases but would get wet and scratched during handling. In a couple of days, the cases would oxidize. It was still used as it was not to the point to be unsafe. In one of our checks, we had to run a finger in the barrel to check for stuck projectiles. The chambers were always smooth as glass which leads me to beleive that the abrasive oxide polished the chambers. They were changed often enough so that no problems occurred dimensionally but again, that's not your super accurate target barrel either.

I beleive aluminum checks would be all right as they're not exposed often to air and sunlight so the chance of oxidization would be minimal but the chance still exists./beagle

[MeestaSparkle]

Any issues of forming the jackets aside, I'm only concerned with how the aluminum will hold up during firing.

Do you think that a coating of moly or teflon or something of the sort might deal with any galling problems, or any potential problems cause by an oxide layer?

[felix]

It would work if something like those "lubes" you mentioned could be implanted within the aluminum itself, creating an alloy of some sort. Remember, not only the surface is at stake, but the internals as well should the rifling puncture the outer surface. If the alloy were tough enough to resist tear-thru, then, yes, just an outside coating would be sufficient. But then if the alloy was that good, there would not be a need for any coating. ... felix

[Gandolf]

Hi All,

Years ago I ran a stretch press at an aircraft manufacturer, and some of the alloys we used would be strong enough for gas checks, IMHO.

However, that doesn't solve the galling problem. I do think that the galling could be due to the softness of many aluminum alloys. A very hard aluminum alloy might be much less likely to gall.

On the stretch press we used a lube on the dies for what amounted to drawing the aluminum. Some a material that had the physical properties something like a cross of a grease and a soap. We also used a moderately heavy oil as a lube.

Ocassionally a problem would arise where the aluminum would not stretch enough to form the part (I worked primarily at making some of the airplane exterior skins), and they would anneal the aluminum to soften it and make it much more stretchable and workable.

Another section that was close to where I worked was the hydropress section. This used a set of metal dies on top of a hard surface that had thin aluminum pieces of sheet metal placed over them, and then a top plate of a VERY thick enclosed rubber pad was then forced over the die with a huge hydrolic ram. The parts then took the shape of the die, and I am very confident that such a procedure could be used to make gas check shaped objects.

The problem that I see is that an aluminum alloy that is soft enough to form into a gas check shape would be so soft as to rapidly gall on a barrel. An alloy that would be hard enough to avoid galling would be very difficult to form.

Perhaps some different type of lube would solve the galling problem.

The stretching work hardened the aluminum. Heat treatment softened it (the heat treating tanks contained a mixture of sodium nitrate and potassium nitrate as a liquid at about 360 degrees F. I think, but this was back about 1972 or so.) (If there was any oil or paper on the aluminum, the temperature and oxidizing power of the heat treating liquid would really burn it off in a super hurry.)

If a hard and strong aluminum alloy could be annealed and then formed into a check, and then hardend to a fairly hard state, it might make a good check. There are a lot of different aircraft aluminum alloys out there, and one might work well. I suspect that these alloys aren't in the low dollar club. They are available in sheet metal of various thicknesses.

This is probably not a low tech problem, but might be solved with the right alloy in a low tech way.

Anyway, my two bits.

Regards,

Gandolf