Projectile casting

[Artilleryman]

Today was nice and we were able to get out and cast some aluminum Parrott rounds.  They still need to be machined before they go into the ammo chest.

[GGaskill]

Do you have a leading (aluminuming) problem in the bore with these?

Also, why cast if they are going to be machined?  It seems that you could get round bar stock that wouldn't require much more machining than those and you wouldn't have as much potential for porosity and such.

[Artilleryman]

I haven't noticed any problems with "leading".  The lugs in the casting at the bottom engage the rifling as a mechanical fit.  The bar stock and machine time to get the lugs on each projectile would be cost prohibitive, at least to me, and time consuming.  Depending on how accurate I want these to be the only machining that has to be done is to turn the two bands on the projectile to bore diameter with just enough windage to keep it from getting stuck when loading and cutting the sprue off.  My cost besides my time is propane and a new crucible from time to time.  We figured today that since 1980 we have cast somewhere around 4 tons of aluminum from scrap, all of which has been given to me by my friends.  I like to think that I am shooting "green" by recycling. 

[Zulu]

Four tons since 1980?  WOW!  That's a lot of shots!  At this point, I have to think you know the best way to do this.
Zulu

[GGaskill]

Didn't notice the lugs.  That would complicate things somewhat.

[cannonmn]

How does the weight of the Al projectiles compare with original wt.?  If lighter, does that limit range or accuracy?  What's the max range to which you can fire them accurately?

[rampa room artillery]

what does your furnace look like to melt al.  or is it easier then i think?  1200 degrees, that twice the temp of lead.   

[Artilleryman]

How does the weight of the Al projectiles compare with original wt.?  If lighter, does that limit range or accuracy?  What's the max range to which you can fire them accurately?

This aluminum projectile weighs about half the of the original projectiles and this projectile has more volume than the original saboted projectile.  The problem with an aluminum projectile is its light weight.  If you put enough powder behind it to get distance the back end of the projectile tries to catch up with the front and the accuracy is terrible (sometimes worse than terrible).  If you reduce the charge to stabilize the projectile you have a howitzer like trajectory and difficulty reaching the target at longer ranges.  Accuracy at 200 yards with a light load can produce six center to center groups.  Probably reasonable accuracy out to 250 to 300 yards.  Anything beyond that you are probably better off with a full weight projectile and a service load.

[Artilleryman]

what does your furnace look like to melt al.  or is it easier then i think?  1200 degrees, that twice the temp of lead.

If you were ever in a high school metal shop (in the old days) you most likely saw a foundry furnace in the back corner of the room next to the welding area.  I am using a discarded high school foundry furnace.  Once the furnace is hot we can pour five to six projectiles and hour from scrap.  Faster if the metal is in ingots (recovered projectiles).

[Artilleryman]

Four tons since 1980?  WOW!  That's a lot of shots!  At this point, I have to think you know the best way to do this.
Zulu

Probably 3000 lbs of zinc also.

[GGaskill]

the back end of the projectile tries to catch up with the front and the accuracy is terrible (sometimes worse than terrible).

A reason to consider machining from solid instead of casting.

By the way, what are you using for a crucible?

[Artilleryman]

We are using a clay graphite crucible. 

[cannonmn]

Has anyone tried casting an aluminum projectile with a cavity in the front end which is then filled with, say, lead.  Idea is to make them heavier while moving the center of gravity forward.  If it worked, recovering them, you would first melt the lead out of them, then melt down the aluminum.

[Artilleryman]

Has anyone tried casting an aluminum projectile with a cavity in the front end which is then filled with, say, lead.  Idea is to make them heavier while moving the center of gravity forward.  If it worked, recovering them, you would first melt the lead out of them, then melt down the aluminum.

Some time ago competition rules allowed 3 inch rifle projectiles to increase in weight to 100 oz.  Shortly after that we started drilling and lead filling our projectiles to increase the weight.  This allowed us to increase our velocity some.  It is my opinion that in order to use more powder to achieve higher velocity with accuracy the projectile needs to weigh 8-10 lbs.  Doing this adds about 20 minutes per projectile to make them. 

[Artilleryman]

Busy again today casting another 29 Parrott projectiles.

[KABAR2]

This photo shows the lugs much better it was hard to make them out in the first photo...... nice work are you sand casting these?

[Artilleryman]

Three piece steel mold.  We turned over 150 lbs of scrap aluminum into something useful.