Using Alum for Gas Checks and Alum Oxide

[RedHawk357Mag]

I was talking with a guy about using Alum GC and he mentioned a concern about Alum Oxide being a problem. I looked Alum Oxide up on Wiki and my eyes glazed over with all the info about it there. This was half way down the page:

"Aluminium oxide is used for its hardness and strength. It is widely used as an abrasive, including as a much less expensive substitute for industrial diamond. Many types of sandpaper use aluminium oxide crystals. In addition, its low heat retention and low specific heat make it widely used in grinding operations, particularly cutoff tools. As the powdery abrasive mineral aloxite, it is a major component, along with silica, of the cue tip "chalk" used in billiards. Aluminium oxide powder is used in some CD/DVD polishing and scratch-repair kits. Its polishing qualities are also behind its use in toothpaste. Aluminium oxide can be grown as a coating on aluminium by anodising or by plasma electrolytic oxidation (see the "Properties" above). Both its strength and abrasive characteristics originate from the high hardness (9 on the Mohs scale of mineral hardness) of aluminium oxide."

So...is there additional steps to ensure that this isn't a problem? Is this a non-issue? Is there anything that can exacerbate the formation of this oxide? Thanks for any insight as I am total lay person on metal issues.

[elwood4884]

I have sold hundreds of thousands of aluminum gas checks and have yet to hear of any issues related to aluminum oxide. I am not sure where this originally started but I have heard it before.

I guess my question would be is how is aluminun oxide formed as it relates to the use of gas checks. Is it caused by heat? We anneal checks all the time without changing the molecular composition of the metal. Is it contact with burning powder? Wouldn't that change the molecular composition of the brass too?

Any metal heads out there have any more info? I am gonna send this to a buddy of mine that works as a chemistry professor at a local university here.

[longbow]

This issue keeps coming up and while the aluminum oxide issue is real and aluminum oxidizes easily, the oxide layer is extremely thin and fine so is likely not doing anything more than extremely fine lapping... if anything.

Then consider that the boolit/check are sized and lubed so oxide if present should be largely removed during sizing and the now clean check is polished and covered with a lube coating (no oxygen = no oxide).

Then the whole works gets seated in the cartridge so again scraping the aluminum check inside the brass cartridge.

I do not shoot a lot of checked boolits anyway but from what I have seen and read there is no issue to worry about.

I strongly suspect that far more barrel wear and erosion occurs shooting full power "J" bullet loads, at least in high pressure bottleneck rifle cartridges, than will occur from shooting cast boolits with aluminum checks.

Just my opinion of course.

Maybe we will get some results in 5 to 10 years when someone has shot enough aluminum checks through a gun to compare to wear/erosion from "J" bullet loads or other cast boolit loads.

When I read about some varmint guns being shot out in a few thousand rounds I would be more worried about that than aluminum checks on cast boolits.

Longbow

[elwood4884]

Well put.

[.30/30 Guy]

+1 for Longbow. Better than I would have said it.

I have put about 10,000 aluminum checks down the tube of my .30/30 and looking to many more.

[JonB_in_Glencoe]

I have heard the Alum Oxide theory before, and think it's a bunch of bunk. I have read why it's bunk, but I am not smart enough to convey the reason why.

ANOTHER thought is...
The Aluminum material I use when making my GC's at home, usually have some kind of coating on them, as seen below, I form them so the coating is on the outside. That coincides with Longbow's comment,

"Then consider that the boolit/check are sized and lubed so oxide if present should be largely removed during sizing and the now clean check is polished and covered with a lube coating (no oxygen = no oxide)."

[Sensai]

Diamond is one of the hardest substances known, and is pure carbon. Graphite is carbon. Using the same thought process that has been used on aluminum oxide, graphite will destroy your gun. The same can be said of molybdinum disulphide and any number of the lubricants that we use.

If you have bare aluminum in air, or any oxygen rich environment, you WILL get a coating of aluminum oxide on the surface of the aluminum. This is a very thin coating because the layer of aluminum oxide insulates the bare aluminum from further contact with the oxygen. It takes a physical or chemical disruption of this thin layer to get the formation of any more aluminum oxide. That's why we have to pass a current through a bath that is in contact with the aluminum to "anodize" the aluminum and get a thicker coating of aluminum oxide for greater protection. In order to get aluminum oxide to form crystals that could harm your barrel, you would have to create an environment with free aluminum ions or radicals and free oxygen atoms in a medium condusive to crystal formation. We don't even come close with either the formation or use of our gas checks.

Sorry for the long windedness (is that a word?), but entirely too much disinformation is out there on this subject. A chemical compound can have MANY different characteristics, depending on it's physical form.

[Dutchman]

Sorry for the long windedness (is that a word?),

Why yes it is! http://www.merriam-webster.com/thesa...ong-windedness

And an excellent supplement to the pool of knowledge.

Dutch

[RedHawk357Mag]

Thanks everyone for some insightful information. Much appreciated.

[armprairie]

I can remember this issue coming up 50 years ago in the Herter's catalog. Herter claimed that aluminum cleaning rods would wear the rifling out of gun barrels, so you should buy the wooden ones he sold. Of course everything in print is true to a kid, so I remember ordering a wooden .22 cleaning rod from them. Such claims are not so easily believed when whiskers are gray. I believe some artillery rounds have aluminum driving bands. Still I prefer copper of course,but if the cost difference is significant, well...

[RedHawk357Mag]

Well...planning on using them in Rugers and if what I have been reading on fire lapping constrictions out of Rugers is anywhere close to the truth I shouldn't have any issues for the next 50 to 60 years Much appreciated Armpraire.

[petroid]

As has been stated aluminum does oxidize and an extremely thin layer forms on the surface. This is only a few atoms thick as the oxidized layer forms an impenetrable barrier to oxygen, unlike oxidation of iron which, as we know, continues unchecked unless removes and a physical or chemical barrier is applied. Mercuric salts, on the other hand, will cause aluminum to continue to oxidize and this will occur at an exponentially increased rate. This is why mercury is not allowed on airplanes. If it makes contact with aluminum, it can destroy the entire aircraft.

[maglvr]

"Is this a non-issue?" Yes.

[RedHawk357Mag]

Maglvr, you forgot to say....bottom line upfront..."Is this a non-issue?" Yes. Again thanks all who weighed in on this question.

[PatMarlin]

THAT us the coolest looking mold I have ever seen.

[JonB_in_Glencoe]

THAT us the coolest looking mold I have ever seen.

Pat,
JTknives really did a great job with this design all around...He did have a lot of input from many forums members for the boolit design. The mold block design is just plain excellent as well. Small enough for the small boolits, a great sprue plate design as well. And of course the engraving is too notch
http://castboolits.gunloads.com/show...MetalMolds-com

[Sonnypie]

Then consider this:
If one considered an aluminum gas check Abrasive...
And laid awake pondering bore wear...
Sleep well in knowing they are self cleaning as they slide down the bore.

That said, I think I shall go ponder the moon falling out of the sky.

[Sagebrush7]

Sonny, when did they let you out?

Then consider this:
If one considered an aluminum gas check Abrasive...
And laid awake pondering bore wear...
Sleep well in knowing they are self cleaning as they slide down the bore.

That said, I think I shall go ponder the moon falling out of the sky.

[yonky]

Sonny, I for one have missed you on the forum , it's nice to have a laugh, where have you been?
I'm sure everyone would like to know? Abducted by alians perhaps ?

[EOD3]

I can remember this issue coming up 50 years ago in the Herter's catalog. Herter claimed that aluminum cleaning rods would wear the rifling out of gun barrels, so you should buy the wooden ones he sold. Of course everything in print is true to a kid, so I remember ordering a wooden .22 cleaning rod from them. Such claims are not so easily believed when whiskers are gray. I believe some artillery rounds have aluminum driving bands. Still I prefer copper of course,but if the cost difference is significant, well...

The more things change, the more they stay the same...

Now it's anything on the internet but it's not limited to kids anymore.