Turned cases?

[gvnwst]

I have a friend who wants to make a rifle in a custom cartridge. The only problem is, the head of this thing is like 1 inch, or more! He found this artical about making brass, but was wondering if he could turn some on a lathe. Is this possible, to buy some brass bar stock, and literally turn out some brass? The custom brass maker he talked to told him some $20+ per case, with a mininum of 1k cases, something he can't afford. But he has access to a lathe that he can use for free.....? (well, he can have someone use it for him, but for free)

So, basically, is it possible for him to design the case in CAD, and have the shop turn them out? I don't know all that much about lathes, so i couldn't answer his question.
Thanks.

 

[servantofinari]

I know it is possible to turn a flat brass disk into a casing, just like you can turn it into a French horn. But as for a “bar” I don’t know. But yah look into the making of brass instruments and see if that helps.

 

[Jim K]

Sure, you can drill out the bar and turn it to any shape you want. It is a time consuming process, but is what some custom cartridge makers do, which is why their cases are so expensive. You can also do what "servantofinari" suggests and work flat brass into a cylinder, a technique called spinning but that might not make a strong enough case.

If the cartridge case is that big, be careful of going over a .50 caliber bore and getting into conflict with federal law.

Jim

 

[gvnwst]

Jim--thanks for the help. I don't know what kind of machine (lathe???) one would use for "spinning", but if the sheet were thick enough, it would probably work.

For what he is wanting to do:
http://thehighroad.org/showthread.php?t=394130
We designed that a few years ago. It is still very legal, thankfully

 

[rcmodel]

O.K> Step away from the lathe right now, before somebody gets hurt!

In the other post, you said:

Caliber: .458
Bullet weight: 550gr-600gr
Muzzle Velocity: 3,250-3,500fps
Ballistics are better than the .408 Cheytac, .50 BMG, and .416 Barrett.

You are talking MAJOR Pressure to get that kind of velocity out of a 550 - 600 grain .458" bullet!

First, drawn brass cartridge cases are far stronger then anything you can make on a lathe out of brass bar stock, for several reasons:

1. They use "Cartridge brass" to make them, not free machining brass as bar stock is made from.
2. Drawn cases are "forged" if you will, so the grain structure flows & follows the shape of the case head & primer pocket.
3. The drawn cases are annealed and differentially heat-treated to make the head area much harder & stronger then the neck / shoulder area.
4. Any .458" caliber round with over a 1" case head would present incalculable bolt thrust on any action it is fired in. Bigger piston, you see!
You are talking 20mm cannon action forces there.

Sounds like a bad idea to me unless you can find a factory made case big enough to use for a basic starting point.

Lathe turned brass bar stock certainly would not be up to the task!

rc

 

[jerkface11]

Just start with 20mm cannon shells cut them off neck them down and turn the necks. In fact that cartridge has probably been done already since ANY wildcat you can think of has already been done.

 

[gvnwst]

rc,

Sounds like a bad idea to me unless you can find a factory made case big enough to use for a basic starting point.

14.5x114. I know where to get it, it is just steel case (forming this is hard i am told), and the brass maker my friend talked to wanted something out of his price range. For now.

1. They use "Cartridge brass" to make them, not free machining brass as bar stock is made from.

That is something i was going to ask, can i get cartridge brass in bar form? If i can't, what would you suggest as a more cost friendly alternative to custom brass?

4. Any .458" caliber round with over a 1" case head would present incalculable bolt thrust on any action it is fired in. Bigger piston, you see!
You are talking 20mm cannon action forces there.

Yes, i know. My friend knows too. He will be purchusing a custom action designed specifically for this.

Just start with 20mm cannon shells cut them off neck them down and turn the necks. In fact that cartridge has probably been done already since ANY wildcat you can think of has already been done.

Actually, we can't find anyone else who has. I was contacted by someone who had the same idea at around the same time, but neither of us have actually made rounds or a rifle. And i stated the reason we didn't start with the 20mm, i couldn't find anough info on it, and we are actually cnsidering making it out of a smaler case than the 14.5. 20mm is bigger.

 

[rcmodel]

14.5x114. I know where to get it, it is just steel case

I see!

Well U.S. 20mm & 30mm cannon cases are steel too, not brass.

Reckon theres a reason for that beside steel being cheaper??

Back in the day, small cannon cases were made of brass, but had corresponding low velocity.

rc

 

[gvnwst]

Are you meaning to say that steel you can have higher pressures (and so higher velocity) with, or was that just a retorical statement?

If normal brass bar stock won't work, where can i get cartridge brass in bars, or what is another way to do this?
Thanks.

 

[jerkface11]

Ask on www.accuratereloading.com in the wildcat forum. They'll point you in the right direction.

 

[gvnwst]

Hmm...right now it is down, or i can't access it. But I'll try later, thanks!

 

[Zak Smith]

Caliber: .458
Bullet weight: 550gr-600gr
Muzzle Velocity: 3,250-3,500fps
Ballistics are better than the .408 Cheytac, .50 BMG, and .416 Barrett.

I just played with QuickLoad a bit for this idea. For a 600gr .458" bullet, starting with the water capacity of 50BMG, the best it thinks you can do with a peak of 60kpsi is about 2900-2950 fps (using 50BMG powders). Doubling the case capacity only increases this to about 3000 fps. The problem I think will be finding a powder slow enough.

 

[Dean Williams]

gvnwst:
If normal brass bar stock won't work, where can i get cartridge brass in bars, or what is another way to do this?
Thanks.

I've done a lot of machining, and use quite a bit of brass, but I don't know of a common source for cartridge brass in anything other than sheet or plate.

When factory cases are made, they start with a bunch of plugs punched from plate, and from there a plug is pressure formed in many steps to form the basic shape of the case. Cartridge brass work hardens like crazy, which is what makes it suitable for cartridges. It gets harder as it is worked.

It starts out with a higher tensile strength than free machining brass to begin with, and it has quite a lot more yield strength than free machining brass. Working it through the case forming steps increases it's hardness, and probably it's tensile strength too.

There's not much you can do on a lathe to increase the strength of free machining brass. If you make cases from it, it will still have it's basic strength characteristics, which is probably way low for what you want to do. I wouldn't trust it for anything in a high pressure cartridge. Yield pressure is only 45k lbs.

Similarly, if you just turned cartridge brass to shape on a lathe, you leave out the forming pressures needed to work harden it.

 

[rfwobbly]

RC and Dean are correct. Cartridge cases are deep drawn from a plug of brass. The resulting case has much higher strength than "free machining" brass stock could ever achieve. My friend, you have stepped into the realm of metallurgy, an engineering science not to be taken lightly when safety is involved.

The people who manufacture cartridge cases probably keep a couple of these guys on staff with masters degrees (or better) and a PE license. These guys are continually grabbing cases off the production line to use as test subjects to make sure that the finished cases far exceed the strength requirements for the pressures. Then, they most likely have to sign their name on each test batch, and those samples and paperwork might be kept for 15 years in case there was ever a question. In short, this is a very serious professional endeavor.

Bottom line: This is not anything you can make at home.

 

[Sunray]

I have an article about making .577-.450 brass out of 3/4" bar stock. The finished brass is not like regular brass inside though. It's just a straight drilled hole.
Your buddy know what a custom rifle costs to have built?

 

[Dean Williams]

I have an article about making .577-.450 brass out of 3/4" bar stock.

That's a good example of something that can be made from free machining brass, (i.e., black powder cartridges).