Hydraulic case forming

[Cap'n Morgan]

Well, I was going to post this in a thread in the Special Projects forum, but the thread got closed. Anyway, it is probably more relevant in this forum so here goes:

I once wildcatted a 6.5x55 to a 7mm Arch. At one point I got tired of wasting expensive powder and bullets on such a mundane task as fire forming the cases (also, every once in a while the case would stretch at the base, ruining the case) On a whim I decided to try using hydraulic pressure to form the cases. I made a simple closed die, using the chamber reamer, with a reamed "smooth bore" for a couple of inches. The case was filled with water and a slip-fit steel dowel inserted through the bore. A solid whack on the dowel with a two-pound hammer and the case was expanded to fit the inner shape of the die. As a bonus, the primer was ejected in the process :wink:

Here's a couple of drawings that should be pretty much self explaining:

http://i1370.photobucket.com/albums/ag248/driftwood4/Capture1_zpsyllk77jh.jpg
http://i1370.photobucket.com/albums/ag248/driftwood4/Capture2_zpsxxc2bc0u.jpg

http://i1370.photobucket.com/albums/ag248/driftwood4/Capture3_zps2mushrpm.jpg

The forming die can be made from and old barrel or similar. I used the left-over from the barrel blank which I had already chambered to test the reamer.

A few pointers.

You'll need at least one or more drain holes in the shoulder area to help trapped air and water to escape. These holes should not be larger than 2mm (.08") or you may risk the pressure punching a hole in the case!!

The piston can probably be any size from 1/4" to 3/8". As far as I remember I used a hardened 8mm ejector pin with a soft head. A smaller-than- caliber piston may be preferable as it can enter into the case without damaging the neck.

The bottom part can be threaded to the die, but I just placed the die on the base plate on some solid surface.

I never got around to put any seals or o-rings in the contraption. The expanding takes place before the water has time to evacuate along the piston/case, but some sort of water resistant grease may improve things. At any rate, you may wan't to be outside when doing this!

Although the cases expand quite well - maybe to 90-95% of the final shape, the outside radius on the shoulder will first be fully formed after the case has been fired once. When I fire formed my 6.5x55 cases they would remain the same length or even stretch a tad. When hydraulic forming the cases would actually be reduced in length (about .04") indicating a more uniform stretching of the brass.

I expanded the case necks to 7mm before forming them, but I guess it would have been enough to just flare/bell the case neck to fit the neck of the die and then let the water pressure expand the rest of the neck.

Hope some of you can use some of this and fell free to suggest any improvements. My project was basically an improved cartridge, and didn't need all that much forming to begin with, but the principle should work just as well with some of the more radical case expansions - like some of the 30-30 wildcats.

[EDG]

I have about got a bucket full of .303 British brass stretching in my #4 Mk 1. I think my cases would last longer if they fit the chamber better when fired the first time. I would not mind blowing the shoulder out and forward with a hydraulic die.
Then I could push it back for a precision fit in the chamber.

You can increase the PSI applied to the water by using the smallest diameter ejector pin that will generate enough volume.
The energy from the hammer is allied to a smaller area.

If you design a die that locks and seals the case into the die with O rings, you could use a hydraulic press to form the cases.
You would also need an O ring on the ejector.
If you use a hydraulic press be sure to put a safety shield around the die in case you split it causing shrapnel.

[n.h.schmidt]

I think the idea has a lot of merit. I could save a lot of case stretching for that first shot. The 303 is a great example of good use for this. The shoulder of a unfired 303 case is short by about .055 to .060 from filling out the chamber . Blowing out the shoulder from firing stresses the case at the web. A regular 303 sizer die could be used for for this water based blowout. You would need a base like the picture shows with a pocket deep enough to allow the case shoulder to have the space needed to expand into. In place of the decapper and expander rod assembly a bolt to fit the die threaded hole on top could be used. A 1/4" hole or larger drilled through that for the close fitting rod.
n.h.schmidt

[Dframe]

Clever idea for the folks who hate fireforming and need a project anyway.

[ray h]

This type of form die has been around for a long time.For those who don't have the tools, Hornady will custom make them for you. Get in touch with Ben at Hornady.

[Ballistics in Scotland]

They have, but I think they were called a hydraulic decapper.

I believe that would have to be air rather than water between the case and the die shoulder, for water wouldn't be forced out in the very brief timespan provided by a hammer blow.

I don't think a commercial .303 sizing die would be large enough for most oversized chambers. New brass us usually pretty close to die dimensions. A neck size or bullet seater die might work better. Otherwise you would need a reamer to make it, and a bad chamber reamer would cost just as much to make as a good one.

As has been said, using a pump would require a very good seal, while a hammer blow wouldn't. O-rings are resilient and the chances are that you would form a neck that wouldn't come out of the device chamber. I think the device would work better with the hammer, if the piston extended through the case neck, and made its good-enough seal there. Just fill the case to the bottom of the neck, insert it in a dry and vertical die, and whack it robustly. Excaping water wouldn't be in the neck-to-steel joint already, and its path would change direction a lot more than with the shorter punch illustrated. Fast moving fluids don't like to change direction, which is why the gases from your revolver don't exist the cylinder gap with a plaintive whine, as they would if you simply tried to pump the bullet down the barrel.

[phaessler]

+1 ray h, Ben is a good contact at Hornady. I always wanted a set but the price was a bit more than fireforming.