shutinlead
01-15-2019, 02:42 PM
My latest project involves considerable fireforming so I thought I’d share some of the processes used. The cartridge isn’t a high-pressure cartridge like so many today, but I have used most of these processes for the same. I'm making 44-85 Wesson from 9.3x74R Brass – this is a cartridge that comes from the era of black powder, vintage rifles, and cast boolits – I’m using this in a high wall and with both black and smokeless equivalent, cast and PP boolits - so it’s fitting. I made the chamber reamer and the dies so some of this is not exactly as per what Donnelly described in his book.
The case is nearly a straight wall, in my design it came out to about .005/6" difference from head to mouth and the case length is 2.85". I've made a few wildcats that were classified as a straight wall but they generally have about .015" or more worth of body taper. The head dimensions of the 9.3 originally measures .464 (spec is .469) Donnelly gives a spec of .472 for my cartridge head and a mouth dimension of .460”. The bullet I need to shoot in my .44 barrel needs to be a .4465 to .447” diameter so in order to make the case to the specs it would only give me a .006 to .007 mouth wall thickness – not favorable to me. I prefer to have a .008 to .009 wall thickness and following the fire-forming process my wall thickness ended up .010 to .011”. In the end, I had to turn the necks on my cases and set the target dimension at .463”. This is getting a little ahead of myself, but a fireformed case coming out of my test chamber and my rifle chamber, measures .472” at .300” in front of the rim and the mouth ends up at .465” diameter.
My traditional way of fire-forming a case is to use 4 to 9 grains of Bullseye, (case size dependent) topped with cornmeal and a compression factor of two hands applied to a wooden dowel… I leave about 3/8” from the mouth to the top of the cornmeal – this gets sealed then with hot glue. In most cases, I use pistol primers because like the Bullseye I – I have it in extreme quantities from a passion long since passed.
To center the case for fire forming, I cut a piece of masking tape and do a single wrap right at the head- it saves having to hold a gun vertical while forming…
Another note on these long cases, before starting anything I annealed my first batch of 25 using a rotary machine I made, the next 50 I annealed by hand, holding each by the rim and turning them in front of the torch – when it got hot, I quenched it in a can of water. I made a tapered expander that started the sizing process – I found this gave me a more consistent forming process. The first 25 I did, didn’t get quite the form I wanted in the chamber so they got the powder and cornmeal process twice. The next batch I had the “hands on control” amount of annealing and they formed much better.
I have loaded and shot the first 25 rounds at the time of this post, 15 were with a grease groove boolit over a calculated load of smokeless and 10 paper patched were loaded with Goex Cartridge black. The distance was 100 yards, from a bench with sandbags and a makeshift scope mount I clamp on the barrel for load testing purposes (still prefer to use iron sights in competition). The smokeless and greaser, gave me a group close to 2 minutes- I was pleased with this thinking it’s a good start with potential. The loads of black caught me off guard, I expected similar results. My first two shots from a clean barrel, impacted about 6” left of smokeless load. I wiped the barrel with two wet patches, then a dry following these first two shots. I decided to use this wiping process for the next 8 shots - between each shot. To my surprise, the group stayed in the same hole with a center to center extreme of about 7/8”. I’ve never had a group shot with black that consistent so we’ll see where this goes - even a blind squirrel finds a nut sometimes. The next batch of loads are ready to go so when time and weather permit - I will attempt to give updates.
234017234018234019234020234021
The case is nearly a straight wall, in my design it came out to about .005/6" difference from head to mouth and the case length is 2.85". I've made a few wildcats that were classified as a straight wall but they generally have about .015" or more worth of body taper. The head dimensions of the 9.3 originally measures .464 (spec is .469) Donnelly gives a spec of .472 for my cartridge head and a mouth dimension of .460”. The bullet I need to shoot in my .44 barrel needs to be a .4465 to .447” diameter so in order to make the case to the specs it would only give me a .006 to .007 mouth wall thickness – not favorable to me. I prefer to have a .008 to .009 wall thickness and following the fire-forming process my wall thickness ended up .010 to .011”. In the end, I had to turn the necks on my cases and set the target dimension at .463”. This is getting a little ahead of myself, but a fireformed case coming out of my test chamber and my rifle chamber, measures .472” at .300” in front of the rim and the mouth ends up at .465” diameter.
My traditional way of fire-forming a case is to use 4 to 9 grains of Bullseye, (case size dependent) topped with cornmeal and a compression factor of two hands applied to a wooden dowel… I leave about 3/8” from the mouth to the top of the cornmeal – this gets sealed then with hot glue. In most cases, I use pistol primers because like the Bullseye I – I have it in extreme quantities from a passion long since passed.
To center the case for fire forming, I cut a piece of masking tape and do a single wrap right at the head- it saves having to hold a gun vertical while forming…
Another note on these long cases, before starting anything I annealed my first batch of 25 using a rotary machine I made, the next 50 I annealed by hand, holding each by the rim and turning them in front of the torch – when it got hot, I quenched it in a can of water. I made a tapered expander that started the sizing process – I found this gave me a more consistent forming process. The first 25 I did, didn’t get quite the form I wanted in the chamber so they got the powder and cornmeal process twice. The next batch I had the “hands on control” amount of annealing and they formed much better.
I have loaded and shot the first 25 rounds at the time of this post, 15 were with a grease groove boolit over a calculated load of smokeless and 10 paper patched were loaded with Goex Cartridge black. The distance was 100 yards, from a bench with sandbags and a makeshift scope mount I clamp on the barrel for load testing purposes (still prefer to use iron sights in competition). The smokeless and greaser, gave me a group close to 2 minutes- I was pleased with this thinking it’s a good start with potential. The loads of black caught me off guard, I expected similar results. My first two shots from a clean barrel, impacted about 6” left of smokeless load. I wiped the barrel with two wet patches, then a dry following these first two shots. I decided to use this wiping process for the next 8 shots - between each shot. To my surprise, the group stayed in the same hole with a center to center extreme of about 7/8”. I’ve never had a group shot with black that consistent so we’ll see where this goes - even a blind squirrel finds a nut sometimes. The next batch of loads are ready to go so when time and weather permit - I will attempt to give updates.
234017234018234019234020234021