6" aluminum round stock for golf ball mortar

[NitroSteel]

I've not heard anyone talk of making a mortar or cannon out of aluminum.  I have a long piece of aircraft grade round stock I was considering using for a mortar.

Is aluminum strong enough to be used for this purpose?  It's just such a pretty piece of metal, it would be a shame not to make something out of it, IF IT IS FIT.

Thank you,

NitroSteel

[Cannoneer]

NitroSteel, this question has been covered here before, and the consensus among those most knowledgeable (George G., M & T, Dominick C., et al.) on the subject is no, aluminum should not be used to fashion BP artillery out of.

I made a search but couldn't come up with the proper threads on this topic (and I know there are more than a few), but one of the members that can explain the technical reasons why it shouldn't be used will hopefully give you a detailed answer.

[KABAR2]

Aluminum is fine for making model forms for sand casting cannon, but it doesn't have the strength

be made into a working cannon. If I remember right the only hand held firearm barrel I know of that was made of aluminum

was for the Gyrojet and that fired a small rocket propelled bullet so there was no concussive force on the barrel.

[Cat Whisperer]

Aluminum won't handle the stress of combustion - it stretches and hardens.  Example:  shotguns with aluminum frames have steel barrels.

But it would be fun to run a CONTROLLED test to see how long one would last.

[GGaskill]

The strong aluminum alloys are probably strong enough for a black powder cannon barrel but the material never reaches a plateau in fatigue strength; it will eventually fail no matter what.  When eventually is I can't predict.  You would likely be safe for a hundred shots, maybe even a thousand.  Do you know how many shots it will be used for?

[dan610324]

interesting thought

but if you trippled the wall thickness ??

lets say a gb size mortar with an ,5" diameter chamber 2" deep , 1,5" wall thickness .
make it the same diameter all way out to the muzzle ( 3.5" )
1.7"  bore would give .9" thickness of low pressure part of the bore .

couldnt that maybe be considered as safe ?? opinions please ??
wouldnt almost any material be useable as long as it is dimensioned right ??

[Cat Whisperer]

I don't think ANYTHING in aluminum would be safe.  There is a concensus, the principles are clear.

The flexing and the corrosive elements spell doom from the beginning.

But it would be intersting to play with - moving from 'guessing based on similar experiences' what would happen to 'this IS what happened in THIS case'.

[Rickk]

For what it's worth, S&W made a special run of 200 (plus a few extra's) S&W chief specials with aluminum cylinders for the FBI about 15-20 years ago. The barrels were conventional steel. I suspect that if the rifled barrel was aluminum the rifling would die a quick and ugly death.

They were rated for 200 rounds of .38 special, and came with no warantee. They were never sold as a civilian gun due to liabiliy issues. I know they existed because I know of a chief's special that got fitted with one of the "extra" cylinders left over from the special run.

That being said, if aluminum was in general good for making gun barrels out of, I would think the US Military would be all over it. Weight is everything to them.

[Cannoneer]

The strong aluminum alloys are probably strong enough for a black powder cannon barrel but the material never reaches a plateau in fatigue strength; it will eventually fail no matter what.  When eventually is I can't predict.  You would likely be safe for a hundred shots, maybe even a thousand.  Do you know how many shots it will be used for?

George, you have a way with words; I'm stickin' to the recommended types of steel!

[dan610324]

all copper based alloys are also sensitive for hardening until they brake after a while , ok its quite a long while   still they are considered to be one of the better for cannon use . the same phenomen will probably also be with steel . so the question wouldnt be if , but when ??

[Cannoneer]

For what it's worth, S&W made a special run of 200 (plus a few extra's) S&W chief specials with aluminum cylinders for the FBI about 15-20 years ago. The barrels were conventional steel. I suspect that if the rifled barrel was aluminum the rifling would die a quick and ugly death.

They were rated for 200 rounds of .38 special, and came with no warantee. They were never sold as a civilian gun due to liabiliy issues. I know they existed because I know of a chief's special that got fitted with one of the "extra" cylinders left over from the special run.

That being said, if aluminum was in general good for making gun barrels out of, I would think the US Military would be all over it. Weight is everything to them.

Rickk, I read an article some time ago in one of the gun mags that stated that a couple pistol manufacturers had conducted some experiments with titanium barrels, and the results showed the rifling just wouldn't hold up to the wear. I have seen both aluminum & titanium black powder smoothbore guns and mortars being sold on ebay, but that's certainly no recommendation of their safety.

[NitroSteel]

I doubt it would be shot a hundred times, but I don't want it to explode (even once).  I'll scrap the idea.  It's not worth the risk.

Nitrosteel

[GGaskill]

Wouldn't almost any material be usable as long as it is dimensioned right??

I guess it would be just as usable as modern artillery is usable but they have to keep accurate track of how many rounds and at what power level they are fired and a barrel is taken out of service once it reaches a set total amount of use.  The remaining problem with aluminum is no one has done enough testing to determine where that out of service line should be drawn.

With steel or bronze barrels, the fatigue failure line does go horizontal and there is a point where essentially an infinite number of rounds can be safely fired.  Now you will find that high power rifle barrels are well below the infinite line but they become useless long before they become dangerous from fatigue failure.  Same thing with bronze barrels; they become non-functional as useful artillery pieces before reaching the fatigue failure point.

[dan610324]

probably an smart decission
but it would be interesting to make some experiments  

[Victor3]

but it would be interesting to make some experiments  

 Problem with the various aluminum alloys (and the various conditions each can be had in) is that there's a range of properties between them that can have much more of an effect on an aluminum golf ball mortar's life expectancy than one made out of just about any old steel.

 Is your test mortar going to be made out of a chunk of mystery metal that you found at the scrap yard, or a piece of 2024 that you know has been aged or solution treated to a condition where the material is less likely to crack after repeated firing?

 Either way, I think any reasonably well designed aluminum golf ball mortar is still going to be working fine long after you've run out of money for powder trying to make it fail.

 (Unless you load it with 1/2# of FFFFG and a lead ball) 

[dan610324]

why use a lead ball when a 24k gold ball is 50% heavier   

[Cat Whisperer]

why use a lead ball when a 24k gold ball is 50% heavier   

Uh oh.  This will degrade quickly to depleted U-235.  (pun intended).   

[Victor3]

why use a lead ball when a 24k gold ball is 50% heavier   

Uh oh.  This will degrade quickly to depleted U-235.  (pun intended).   

 

 Oh come now....We're not that dense, are we?

 I'll stop at tungsten.

[dan610324]

dont forget the enviromental aspect , lead and uranium is not good .
so gold or tungsten is the way to go