Cylinder she'll complete

[Merlin]

I have finished my first "traditional" 3" cylinder shell. I am curious as to whether the dimensions are within acceptable limits. The shell measures 6" in height and 2.87" in diameter.. It weights 21 ounces which is much heavier than a 3" ball shell.

Now when considering the lift charge using the rule of thumb of one ounce BP per lb. of shell for small shells I get 37 grams a little more than I use for a 4" ball shell.

Am I missing anything? That's more lift than I have used in any 3 or 4 inch ball shell. Generally, wihen reloading center fire cartridges, as the weight of the projectile increases the powder charge decreases in order to keep pressure within limits.

Are increasing lift charges with increasing shell weight acceptable, to a point, because the shell fits loosely in the mortar where the bullet seals the rifle bore?

[Mumbles]

That is fairly long and heavy for a 3" shell, but I have no reason to suspect it wont function, assuming it was well made. What all is inside of it? My 3" cylinders tend to come out around 6-8oz typically for a single star break. I've fired multi-break shells up to about 50oz though with success.

 

If you're concerned about under lifting, you can always round up or add a little more. This is actually a very common practice, but rarely talked about or perhaps just assumed/taken for granted. I almost always round up to the next ounce or at least half ounce. If you look at actual tables of lift given in Fulcanelli or in some of the BAFN books, this becomes more obvious. They list lift charges for 3" shells as 1oz of 2FA, and 4" shells as 2oz. Both of those figures are approximately twice the ounce per pound "rule", or incorporate an unspoken generous rounding. I've never had to go to those extremes, but also have almost always used hotter than commercial BP.

 

You do sort of use a diminishing amount of lift in shells with increasing weight. With small to very small shells, you tend to need probably anywhere between 10-25% w/w to lift them. As you advance into somewhat larger shells, over a pound or two lets say, then you reduce it down toward 6.25% w/w (oz/lb). As you get into very large shells, the amount drops a bit more. I don't have exact figures, but lets say 5% for a shell that weighs 20lbs. There are some special circumstances where you can you substantially less, but that involves pretty heavy shells and a different lifting method.

 

For color breaks I tend to make the shells "square", or about as long as they are wide. For a 2.5" ID casing, I tend to fill about 2.5" high. This results in a shell probably a bit under 3" long or so after disks, pleating, pasting, etc. I was told somewhat recently that even this isn't correct, and that the proper way to build them is to use a shorter interior so the final height is approximately 2.5" tall all said and done. My shells have always worked fine for me however. It always made more sense for the explosive cavity, for lack of a better term, to be square and let the string, paper, and stuff do what they will. Maybe I'll do some comparisons some day.

[dagabu]

Good points Mum. Reading and watching some videos, I found that the desired height is about 1:1.2, width:height. As explained by an Italian, the shell becomes a ball right before bursting. Any longer and the stars on the bottom/top end up in a mass and not spread out.

[Merlin]

Thanks for the detailed answers. I didn't have a actual former - used a spray can. I called myself researching the dimensions but I didn't find anything definite on the length. But it does now make sense it might not have much symmetry. The BP burst is 5 FA and occupies the canulle top to bottom for total of 80 grams. I used 5 FA to get the most powder for burst but I suppose there may be a problem with flame propagation. There is nothing added to the BP. My goal is to use only BP for bursting. I am not much concerned about a low break because it is filled with 1/4 inch stars and left over micro crackle all which burns pretty quickly. I try -then I learn how to do it. I will need to make height 3-4 inches on the next one. My spiking will probably need improving as well. I will get there. My real concern from a safety aspect is the weight. I knew when done it was too much and I used time fuse instead of spollette and though I used a end cap over the fuse to protect it since I used wheat paste a little concern for moisture getting to the fuse- as they say in golf -4! I rationalized it should be safe to fire as multi-breaks can be in the same range. I used small stars to be sure they burn up if it breaks low.

Thanks for the comments. I will adjust things.

Edited August 3, 2016 by Merlin

[dagabu]

Well, yes and no. No SINGLE shell is that tall. Each break has 4 disks. This allows for a much stouter she'll and can hold up to the lift.

[Merlin]

Hum... I may have made a star mine the hard way. Maybe I won't fire it just mount it as a reminder of just how steep my learning curve is really. Makes sense the structural integrity is lacking. Live and learn but at least live. Thanks Dag.

[Mumbles]

It might hurt, but you can always disassemble and make a new shell or probably two.

 

There are some issues with overly long shells. The biggest is the potential for the shell to buckle or fold in half and burst in the mortar or at the muzzle. This is a factor for long mult-breaks too. Longer shells also tend to be somewhat less structurally sound since they tend to be more compressible.

[dagabu]

Thanks once again Mum for using the right words, I was trying to figure out how to say that as well.

[Merlin]

You guys are right. No loss, just time and I have plenty of that. I will dissemble. No point in burning a pound or more of comp in a fireball. Thanks much for your guidance!

[Merlin]

I disassembled the first over sized shell and made one that totaled 4" in length. Tested it tonight. It worked perfectly. Actually better than any of my ball shells. I will never make another plastic shell. The cylinders may be extra work but they are worth it! The sound and star ignition and symmetry was exactly what I was hoping to get.

I will reduce overall length to 3.2". I don't mean paper ball shells wouldn't be as good but I honestly rather spike than do all that pasting. That's for all the info!