Harry O
01-03-2014, 05:21 PM
1. Pure lead or nearly pure lead with just a little bit of tin does not get frosted, no matter how hot the pot or melt is. It stays shiny. It is also easier to cast with. With antimony, more heat is needed and part or all of the bullet can become frosted with high heat. The more antimony there is, the lower the temperature at which it will become frosted. Bullets that are partially frosted (particularly long .30 cal rifle bullets) are bent toward the frosted area (this can be checked by rolling on a flat surface – a piece of glass is best). Fully frosted bullets are not bent - at least that I can measure. In addition, bullets with high antimony develop white lead corrosion much quicker than pure lead bullets or lead bullets with a little tin.
2. Starting with two mixes that are the same hardness: (1) pure lead with a lot of tin, and (2) pure lead with a little bit of antimony. The one with tin can be driven faster than the one with antimony before leading starts. However, judging the limits of a bullet from leading does not work very well for me. I have found that a much better way to judge a bullets limit is to shoot targets from a rest, working up from low loads to higher loads. When the accuracy disappears, the bullet has failed whether or not there is any leading. The accuracy disappears for me almost always before the leading starts. Of course, the bore smoothness and bullet fit also figure in to when leading occurs.
3. Dropping a bullet with antimony (and presumably arsenic) into a 5 gallon bucket of water will harden it quite a bit (easily over Bhn 20 to nearly Bhn 30). The colder the water, the greater it will harden. The problem I have is the consistency of the hardness. The Bhn can vary a lot from one bullet to another. That does have some effect on the accuracy, particularly when you are near the pressure limits for that hardness. And, that is just when you want the extra Bhn. There are probably several reasons for the variation. Dropping a bunch of cast bullets into cold water will heat the water up. This makes at least a small difference in the Bhn. The length of time between filling the mould and actually dropping it can easily vary which makes a bigger difference on the Bhn.
There seems to be much less variation in hardness when the bullet is dropped onto a towel to air-dry, but the bullets will not be anywhere near as hard. Lack of hardness is not a major problem since I rarely use more than Bhn 15 anymore. I only go that hard for gas-check or +P non-magnum loads. The majority of the bullets I use are Bhn 11 (most non-magnum, non +P loads). My CAS loads are Bhn 6 or 7.
4. Another reason I don’t water-drop cast bullets is that the hardness decreases with age. When I cast bullets I usually cast up a bunch (20 to 40 lbs worth stored in a sealed ammo box) and store them unsized and unlubed. When ready to reload, I will size and lube enough for what I plan to load. I still have some cast bullets that were originally cast 20 odd years ago. I don’t know the average age of the bullets I use, but I would guess maybe 5 years from casting to shooting (that is average, not to the first use). That means that if it had been water hardened when I cast it, it would be soft again by the time I shot it. That introduces another (very important) variable in getting a good load. The hardness of bullets that are air dropped changes very little over the years.
5. It doesn’t work well for me to hold the mould up against the pour spout in a bottom-pour pot. When doing so there is a problem with flashing, internal voids, and consistent weights. The amount of lead in the pot makes a noticeable difference in the finished weight of the bullet when the mould is held up against the pour spout. The more lead in the pot, the heavier the bullet. When the mould is held half-an-inch or so below the spout, the amount of lead in the pot makes very little difference in the finished weight of the bullet. I have tried using a dipping spoon, but have not seen any advantage to it with the bullets I cast.
6. The hotter the melt is kept (within reason), the more uniform the weight of the finished bullet. The key here is keeping the glob of molten lead on the top of the sprue plate liquid as long as possible. If successful, there will be a dimple above the sprue plate hole when the glob hardens (flashes over). Without the dimple, the weight will vary more. However, this means slower casting.
7. When pre-heating a mould before casting, it is as important to preheat the sprue plate, too. A cold sprue plate will cause the molten glob on top of it to flash over too quickly, leading to voids (and weight variations).
8. The more complicated the mould shape, the hotter the pot/melt must be run. Numerous small lube grooves, deep lube grooves, sharp corners, a hollow-point, a hollow-base, etc, all require more heat than a simpler mould. The simplest mould shape is a round-ball. I can cast with a RB mould at fairly low temperatures. Anything that departs from that shape requires more heat.
9. It is pretty useless to hardness test a bullet less than a week or two after casting. Most of the mixes I use take longer than that to reach their final hardness. In almost every case, the hardness goes up with age (for anything with antimony or arsenic in it). Bullets that are dropped into water will reach their final hardness faster. Bullets that are air-dropped will harden slower. In order to know that I will get the bullet hardness I need, I have a bunch or recipes on the wall that I use to predict the final hardness. Of course, that is only for air-dropped bullets.
2. Starting with two mixes that are the same hardness: (1) pure lead with a lot of tin, and (2) pure lead with a little bit of antimony. The one with tin can be driven faster than the one with antimony before leading starts. However, judging the limits of a bullet from leading does not work very well for me. I have found that a much better way to judge a bullets limit is to shoot targets from a rest, working up from low loads to higher loads. When the accuracy disappears, the bullet has failed whether or not there is any leading. The accuracy disappears for me almost always before the leading starts. Of course, the bore smoothness and bullet fit also figure in to when leading occurs.
3. Dropping a bullet with antimony (and presumably arsenic) into a 5 gallon bucket of water will harden it quite a bit (easily over Bhn 20 to nearly Bhn 30). The colder the water, the greater it will harden. The problem I have is the consistency of the hardness. The Bhn can vary a lot from one bullet to another. That does have some effect on the accuracy, particularly when you are near the pressure limits for that hardness. And, that is just when you want the extra Bhn. There are probably several reasons for the variation. Dropping a bunch of cast bullets into cold water will heat the water up. This makes at least a small difference in the Bhn. The length of time between filling the mould and actually dropping it can easily vary which makes a bigger difference on the Bhn.
There seems to be much less variation in hardness when the bullet is dropped onto a towel to air-dry, but the bullets will not be anywhere near as hard. Lack of hardness is not a major problem since I rarely use more than Bhn 15 anymore. I only go that hard for gas-check or +P non-magnum loads. The majority of the bullets I use are Bhn 11 (most non-magnum, non +P loads). My CAS loads are Bhn 6 or 7.
4. Another reason I don’t water-drop cast bullets is that the hardness decreases with age. When I cast bullets I usually cast up a bunch (20 to 40 lbs worth stored in a sealed ammo box) and store them unsized and unlubed. When ready to reload, I will size and lube enough for what I plan to load. I still have some cast bullets that were originally cast 20 odd years ago. I don’t know the average age of the bullets I use, but I would guess maybe 5 years from casting to shooting (that is average, not to the first use). That means that if it had been water hardened when I cast it, it would be soft again by the time I shot it. That introduces another (very important) variable in getting a good load. The hardness of bullets that are air dropped changes very little over the years.
5. It doesn’t work well for me to hold the mould up against the pour spout in a bottom-pour pot. When doing so there is a problem with flashing, internal voids, and consistent weights. The amount of lead in the pot makes a noticeable difference in the finished weight of the bullet when the mould is held up against the pour spout. The more lead in the pot, the heavier the bullet. When the mould is held half-an-inch or so below the spout, the amount of lead in the pot makes very little difference in the finished weight of the bullet. I have tried using a dipping spoon, but have not seen any advantage to it with the bullets I cast.
6. The hotter the melt is kept (within reason), the more uniform the weight of the finished bullet. The key here is keeping the glob of molten lead on the top of the sprue plate liquid as long as possible. If successful, there will be a dimple above the sprue plate hole when the glob hardens (flashes over). Without the dimple, the weight will vary more. However, this means slower casting.
7. When pre-heating a mould before casting, it is as important to preheat the sprue plate, too. A cold sprue plate will cause the molten glob on top of it to flash over too quickly, leading to voids (and weight variations).
8. The more complicated the mould shape, the hotter the pot/melt must be run. Numerous small lube grooves, deep lube grooves, sharp corners, a hollow-point, a hollow-base, etc, all require more heat than a simpler mould. The simplest mould shape is a round-ball. I can cast with a RB mould at fairly low temperatures. Anything that departs from that shape requires more heat.
9. It is pretty useless to hardness test a bullet less than a week or two after casting. Most of the mixes I use take longer than that to reach their final hardness. In almost every case, the hardness goes up with age (for anything with antimony or arsenic in it). Bullets that are dropped into water will reach their final hardness faster. Bullets that are air-dropped will harden slower. In order to know that I will get the bullet hardness I need, I have a bunch or recipes on the wall that I use to predict the final hardness. Of course, that is only for air-dropped bullets.