Aluminum Oxide a Problem?

[Jeff H]

Aluminum oxidization is obviously very hard - it's used in abrasive papers for the specific task of wearing down another surface. After all, they make sandpaper out of it, right?

I have always been under the impression that aluminum oxidizes very quickly and forms a thin "protective" coating on itself so assume that about everything aluminum is oxidized by the time I get my hands on it. The point being that the oxidation is there whether it looks crusty or not.

Anodizing, if I understand that correctly, is a form of induced oxididation of aluminum and is known for being extremely hard too. I am not using anodized stock, but just wanted to reinforce the point of my concern that aluminum oxide is very hard.

So, has anyone of metalurgial merit officially poo-poo'd the notion that we are slowly fire-lapping our barrels into smooth-bores using aluminum checks?

Now, I'm not trying to bust anyone's bubble or rain on their parade here, as I have a GC maker myself and have been very pleased with the resulting components and the control I have over size in terms of compatibility with several different moulds. Since I have been messing with them in a .357 Max. rifle, I have the bug to mess with them in a particular .223 Remington that has an affinity for cast bullets as well. .22 GCs are (were?) cheap, but not to be found and I do like having control over the qulity of my components even just that I could have them when I want, even if under siege as it feels we are currently. I just like making my own stuff as much as I can too.

I am hoping to hear that the oxidation on purchased or scrounged stock is not a concern.

[tjones]

My old man a very wise man used to say to me, a little knowledge is dangerous !

[fishhawk]

well lets look at this. Yes alum oxide is hard and used in sand paper but it is fractured alum oxide so there will be sharp corners that will remove material, is a smooth alum oxide on flashing that's used for gas checks abrasive? I haven't seen evidence of it in my usage yet.

[Jeff H]

My old man a very wise man used to say to me, a little knowledge is dangerous !

Ignorance is bliss?

well lets look at this. Yes alum oxide is hard and used in sand paper but it is fractured alum oxide so there will be sharp corners that will remove material, is a smooth alum oxide on flashing that's used for gas checks abrasive? I haven't seen evidence of it in my usage yet.

Good point and yes, it's smooth but still hard, which is what I wonder about. I know it doesn't feel abrasive but neither does a ceramic sharpener. It may well be absolutely no concern whatever but I wanted to get others' perspective. How much shooting have you done with the alunimum checks? I just started recently and have only aout a hundred of them through a bore that might actually benefit from some controlled abrasion - so I have not seen any signs and wouldn't expect to at this point.

Thanks for the replies.

[Heavy lead]

It may be hard, but with the very thin layer of hard aluminum oxide covering a very soft metal, both in the form of aluminum and lead I cannot see the harm.
That is a completely unscientific observation FWIW.

[tjones]

I'd bet your couldn't file your fingernails faster than they'd grow with the microscopic film of oxide.

[Jeff H]

It may be hard, but with the very thin layer of hard aluminum oxide covering a very soft metal, both in the form of aluminum and lead I cannot see the harm.
That is a completely unscientific observation FWIW.

Well, that's where I'm at on this myself. Seems ok based on my unscientific observations, but are we rationalizing? I'm on board with everyone else's thoughts but just don't know if I am correct in my thinking.

I'd bet your couldn't file your fingernails faster than they'd grow with the microscopic film of oxide.

Agreed. The smoothness of the oxide and the resilience of our nails - might take a while. Still, I couldn't possibly file my nails at 2000 fps. Again, what I am hearing is making sense but based on my own limited knowledge.

[Mooseman]

I have tried to point this out many times in discussions about Aluminum. As a Machinist /Gunsmith and someone who has worked with metals for 40 years I will never put an Aluminum gas check down one of my barrels. As has been stated, Aluminum Oxide forms almost immediately on any aluminum surface and it is what stops aluminum from corroding. It is abrasive , and aluminum oxide will cut hard steel and cut it fast. I use plain aluminum rods to sharpen the hardest Ka-Bar knives by using them like a sharpening steel. It will put a razor edge on a knife. Try it for yourself on an old Aluminum cleaning rod or piece of aluminum tubing.If you cut Aluminum foil with scissors it will sharpen them (google it if ya dont believe me). In our machine shop, we used aluminum bars to hone sharpen hard tooling cutters.
Anodized aluminum has the oxide crystals grown larger and hardened like corundum giving it an even more abrasive surface. Aluminum foil which is about as pure as you can get,has been used for removing rust from chrome bumpers for years , and I have used it to lap barrels with many times, as well as other applications needing a fine abrasive surface.
Getting back to Gas checks, you have several things to consider, not only the Abrasive oxide, but the residue in the barrel combining with the soft aluminum surface under pressure will wear rifling. Another consideration is the contact of Aluminum with brass (which is copper and zinc)
in loaded ammo as it forms an electrolysis between the 2 dissimilar metals, and add to that the acidic environment of gunpowder and over time you are asking for trouble with corrosion , metal Ion transfer, and possible bonding of the Aluminum to the brass case wall. It is one reason why Aluminum is never used against copper in any application.
Extensive Lab tests were done rubbing a steel rod on Aluminum roofing panels and it was determined that the 2 metals would transfer back and forth between themselves and cause wear to both surfaces and they were then photographed with electron microscopes to determine wear patterns and how oxides formed and reformed.
All this Information is out there including tests of hard cutters NASA did for machining parts for The Aerospace program and how some HSS cutters were useless with certain coatings as the Aluminum bonded to them during use, similar to what can happen shooting aluminum down a barrel at high speed.
Ask yourselves this...Why doesnt Hornady or Lyman etc. make AL checks since its cheaper than Copper ? Why are there no Aluminum jacketed bullets ?
Its Has nothing to do with the softness of the material and everything to do with the Abrasive nature of The Oxide as well as how it may react loaded in Brass cased ammo.
Rich

[Jim]

..... Why are there no Aluminum jacketed bullets ?.....

There ARE aluminum jacketed bullets. I dug quite a few of them out of a berm last year when I was cleaning a pistol range.

http://www.ncbi.nlm.nih.gov/pubmed/7114018

[tjones]

Now I know why airplanes can cut though the air so nicely

[Sasquatch-1]

in loaded ammo as it forms an electrolysis between the 2 dissimilar metals, and add to that the acidic environment of gunpowder and over time you are asking for trouble with corrosion , metal Ion transfer, and possible bonding of the Aluminum to the brass case wall. It is one reason why Aluminum is never used against copper in any application. Rich

I am not a machinist nor am I a metallurgist (sp) But I do have one observation to bring up about the above statement. Wth the Blazer aluminum case ammo, why is there not a problem with storing this? You have either a lead bullet or copper jacket touching the aluminum case. I have NO scientific background to fall back on and I am just putting the question out there.

I do not shoot aluminum through my guns but have heard that with the gas check you have a film of lube being laid down prior to the aluminum going down the barrel.

[fishhawk]

The only way this will be decided is with 2 brand new rifles same make same model figure out some way to measure the barrel bore of each and then fire 5000 rounds of each alum and copper gas checks down the barrel then take the measurements again.

[dancingbear41]

There ARE aluminum jacketed bullets. I dug quite a few of them out of a berm last year when I was cleaning a pistol range.

http://www.ncbi.nlm.nih.gov/pubmed/7114018

I still have a number of boxes of Winchester Silvertip. I am going to have to access this article as well! Thanks.

[tjones]

I've cleaned many machine gun barrels, seen cutaways too. Some even had riflings left but generally the first six inches were history.
Anyway it wasn't oxides of anything that blew them away. Just plain old hot gases.

[Hogdaddy]

The only way this will be decided is with 2 brand new rifles same make same model figure out some way to measure the barrel bore of each and then fire 5000 rounds of each alum and copper gas checks down the barrel then take the measurements again.

I'm up for the research, Just Need equipment ; )

H/D

[Case Stuffer]

Every material in the world is abrasive ,period! There is however a great deal of difference in the levels of abrasion and ofcourse the force(s_ applied have a rather large effect also.


Years ago I manufactured a product and during one of the operitions I used a mechanical counter and triped it with my trigger finger. This counter had an aluminum arm on it and within a matter of a few weeks the wear on it was very obvious.

Post # 12 and 14 are both correct,IMO.

I fully realize that movies are not real but I still cringe when someone empties a clip of 20-30 full auto ,reloads and repeats. In the first place what a waste of ammo and second place now barrel is damaged and is only good for Spray & Pray. As I said I know movies are not real and firearms shooting blanks with placed controlled explosives used to show bullet impact but guess what U-tubers do the same thing with their personal firearms.

[ubetcha]

I am not a machinist nor am I a metallurgist (sp) But I do have one observation to bring up about the above statement. Wth the Blazer aluminum case ammo, why is there not a problem with storing this? You have either a lead bullet or copper jacket touching the aluminum case. I have NO scientific background to fall back on and I am just putting the question out there.

I do not shoot aluminum through my guns but have heard that with the gas check you have a film of lube being laid down prior to the aluminum going down the barrel.

I was going to ask the same question.During the lubing and/sizing procedure,there should be a thin layer of lube on the bullet and gas check,providing the check is not wiped clean of course.Should'nt this provide some protection between the brass case and the bullet and with the lube layer on the bore provide some protection for excessive wear? Even if a sharpening steel or sandpaper become clogged up with oil or grease or sanding debris,doesn't that greatly reduce it cutting ability?I'm asking these questions because I don't have an answer

[Jeff H]

OK, definitely some serious thought going into this and all of it seems well founded. How do we test what we (presumably rational beings) are not mistaking conjecture for what we believe to be common sense? I am not trying to discredit anyone's ideas, rather I tend to question my own thinking until I can satisfy myself that I am on the right track - and I AM thinking along the lines of both perspectives presented here.

Mooseman, I particularly appreicate your effort here. That took some time and I am certain you knew you would be compelled to explain some of it, but we'd never get anywhere on anything if everyone had the exact same ideas. Several things I hadn't thought of myself too, like why don't manufacturers make aluminum checks? Dissimilar metals - I have seen instances where there were supposed to be issues but weren't and then where the issues were real but unexpected. I suppose some of that may have to do with conditions.

Aluminum bullets? Yes, this was one of my first rationalizations - Winchester Silvertips. But, I have learned that just because someone makes something doen't mean it's all good, but then again, they have been making these for a long time. I have never heard even a question raised about these and I while live down a dirt lane, I don't live in a cave. That's a single example. Maybe something to hang our hat on, maybe not. Dissimilar metals between aluminum and steel is real. Carpenters hanging gutters and installing aluminum trim see the results. Brass and aluminum? That's one I had never considered but then there's the Blazer ammo thing. On the other hand, how many times have we done something for decades only to find out it was not necessarily ideal? Never mind the Chicken Little Syndrome, there are real examples.

HD, your a every generous to volunteer your time so readily. I might be able to save you some time though. I am shooting the .357 Max. in a H&R Handi Rifle with aluminum checks. The greatest danger I face with that is that I may end up with a smoother, shinier bore, and I will be watching it. So far, I have shot only a handful of RDO 190s at moderate (for the Max.) velocities and the only observation I can share is that after firing twenty rounds I ran a brush through it. I got a significant puff of "dust" out the end when the brush cleared the muzzle. No lead, no chunks, in fact, the bore looked quite good, just a little dull until I brushed it. Ten strokes, ten puffs. Not something I have observed before. Swabbed it with some Break Free and set it muzzle down to await the next opportunity to shoot.

I certainly appreciate the patience on this one. Maybe, as at least one has implied, the energy put into the thought is not necessarily terribly well spent. I'm open to that too but still want to know. Anyone or everyone could be absolutely correct in this matter.

[Jeff H]

I was going to ask the same question.During the lubing and/sizing procedure,there should be a thin layer of lube on the bullet and gas check,providing the check is not wiped clean of course.Should'nt this provide some protection between the brass case and the bullet and with the lube layer on the bore provide some protection for excessive wear? Even if a sharpening steel or sandpaper become clogged up with oil or grease or sanding debris,doesn't that greatly reduce it cutting ability?I'm asking these questions because I don't have an answer

I wondered about that too. The bullets I am shooting now are tumble-lubed. The ones I have just prep'd are conventionally lubed, but I wiped the bases free of lube. I am sure I didn't get it all off, so maybe.....

There have been mild steel jackets in the past too. I have never looked into that too much but wondered if there was any accelerated wear because of them. Probably, but enough to make a significant difference - I don't know. I believe they would have been softer than the barrel steel - but barrels arent particularly hard either.

As far as using two fresh rifles, I agree, but time and funding probably rules many of us out as participants. Disinterest will likely knock many out of the running as well. After all, if it's working, why worry? It's strictly a point of curiosity for me, for one thing, but I also want to make sure I am not screwing something up. Again, the worst I could do is make a less than perfect-looking bore look a little better and should be able to see that. Even if that happens, the process may be self-limiting and actually beneficial.

I will be shooting another H&R with aluminum checks as soon as I can swing another check-maker. I will keep an eye on both. I certainly don't want to make anyone uncomfortable about using them and don't want to ruin the fun and gratification of making our own stuff, after all, I'm invested in the concept myself. The .008" GCs I made yesterday look fantastic and fit two moulds pefectly, so I am excited about using them. I have never liked using GCs in the past and have nly "needed" them on a few revolvers which are history now anyway. Once I started shooting cast in rifles, things changed a bit and GCs made more sense, so I can't just avoid them anymore.

Again, I certainly appreciate the patience on this question. It would be easy to get defensive about it or consider it a waste of time when there don't seem to be bore exhibiting scary symptoms. This is one of the few

[Jim]

Here is a METALS GALVANIC COMPATIBILITY CHART that shows the values of dielectric reactions between various dissimilar metals.