Author Topic: Aluminum Gun Tubes (Read 793 times)

CAV Trooper · « **on:** May 09, 2005, 04:55:23 AM »

Something I've never seen on this board is a discussion about using aluminum to make a cannon or mortar...So here goes.

On the plus side, it's very light (a 4" x 12" round weight 15lbs) which would make transporting a gun lots easier. It doesn't rust like steel and it's easy to weld. One down side is that it can be fairly expensive in larger diameters.

7075-T6 has a yield strength of 73,000psi which is higher than some grades of steel that we currently make gun tubes. That being the case, why isn't it used for cannons and mortars?

The floor is open guys and gals....What say you?

Will Bison · « **Reply #1 on:** May 09, 2005, 06:09:27 AM »

I think aluminium would and does work just fine. As you indicate, 7075 treated to T-6 is some darn tough stuff. I would guess that Al is stronger than cast iron.

I figured up the weight of my steel tubes and then computed the weight in Al. Too light for my use. I prefer steel/iron because it brings up the weight of the gun. The extra weight of course soaks up the recoil better.

Double D · « **Reply #2 on:** May 09, 2005, 07:03:14 AM »

Will said it....RECOIL!!!!

Cat Whisperer · « **Reply #3 on:** May 09, 2005, 07:25:46 AM »

Quote from: CAV Trooper

Something I've never seen on this board is a discussion about using aluminum to make a cannon or mortar...So here goes. ...

Good question.

One issue is that not of strength, but of the characteristic of the metal itself. 'Toughness' or the resistance to being worked and not becoming brittle and breaking is very good in cast iron and extremely good in forgings (to include aluminum). If I'm not mistaken it has something to do with the grain structure and alignment of the larger molecules.

Go one further than aluminum - look at carbon, synthetics and so forth.

You see fiberglass reinforced tubes for lower pressure applications as in the LAW (light anti-tank weapon) rocket launcher.

I've seen .22 barrels with a minimal diamter tube and ends of steel filled in with carbon fiber for strength - and light weight.

We KNOW pvc pipe isn't good - very little strength where it counts.

dominick · « **Reply #4 on:** May 09, 2005, 04:33:35 PM »

7075....can't weld it .....can't bend it... My experience with it was in fabricating a 1/4" aluminum mid plate for a aa/fc drag car. It cuts and machines easily. As far as strength is concerned it was prone to cracks so they (NHRA) changed the rules to use chrome moly steel plate...Dom

CAV Trooper · « **Reply #5 on:** May 09, 2005, 06:03:32 PM »

Good thoughts guys. I agree that recoil could be a real problem due to the light weight. You'd probably have to stake the thing down so it wouldn't end up in the next zip code.

A mortar shouldn't be so bad since most of the recoil is directed downward but I'll bet it would still jump around quite a bit.

Since 7075-T6 is used to make AR15/M16 receivers and also in aircraft construction, I was thinking about using it to build a beer can mortar. Probably the biggest detriment to the project though is the price of the materials. A 5"x12" piece for the tube along with a 1.5"x12" piece for the trunnion costs over $250. Getting is anodized a really nice bronze color would add another $150. Don't think the wife would be real happy with that expenditure right now.

Oh well, back to the drawing board. Let's see, what else can I use? Oh hey...I got it...titanium!!! :wink:

Double D · « **Reply #6 on:** May 09, 2005, 07:09:30 PM »

I would think that the trunnion would not last long from the pounding and flexing of recoil either.