Cap'n Morgan
02-13-2015, 09:33 AM
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.
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.