Great discussion!
I made my own annealing machine that spins a case next to a torch flame. Each case gets the torch applied to the same spot on the neck and holds it in the flame for the same amount of time.
Annealing is both temperature and time dependent. I don't recall the exact numbers I researched so don't quote me, but for cartridge brass it will start somewhere north of 600-650 degF but will require maybe 30 minutes to anneal. As you increase temp the time to anneal obviously decreases.
Down near the head needs the hardness from the factory so it better not get annealed or it will fail.
One problem with a torch method is that both ambient temperature and how full your fuel bottle is will change the size and intensity of the flame coming out. So every time I anneal I start with a dummy cartridge of the same make and size. Adjust the flame accordingly to get the tip right on the middle of the neck. Then paint a stripe of 450 degF tempilaque down the entire length of the body. Next I paint the inside of the neck with 750 tempilaque. Then change the dwell time to ensure the 750 in the neck totally liquifies and also check to make sure the lower half of the case does not get above 450. Simple process control to ensure I get the necks up to temp while not annealing anywhere near the head.
Without a high end micrscope I cannot see the crystalline grain structure to prove that I have annealed the brass. So I use empirical data. Each bullet has the same feel when seating into the case neck. Next, ES must be low for a batch of ammo. All of my brass lasts for around 12-15 reloads. Where it used to only last 5-6 with my max pressure loads before I annealed. Finally, The ammo should be capable of holding 1/4-1/3 moa anywhere between 100 and 1000 yards (or the best accuracy potential of the rifle) and not degrade in accuracy as the brass continues to get fired.
So far this method has given me very good results. High accuracy and high brass life.
I made my own annealing machine that spins a case next to a torch flame. Each case gets the torch applied to the same spot on the neck and holds it in the flame for the same amount of time.
Annealing is both temperature and time dependent. I don't recall the exact numbers I researched so don't quote me, but for cartridge brass it will start somewhere north of 600-650 degF but will require maybe 30 minutes to anneal. As you increase temp the time to anneal obviously decreases.
Down near the head needs the hardness from the factory so it better not get annealed or it will fail.
One problem with a torch method is that both ambient temperature and how full your fuel bottle is will change the size and intensity of the flame coming out. So every time I anneal I start with a dummy cartridge of the same make and size. Adjust the flame accordingly to get the tip right on the middle of the neck. Then paint a stripe of 450 degF tempilaque down the entire length of the body. Next I paint the inside of the neck with 750 tempilaque. Then change the dwell time to ensure the 750 in the neck totally liquifies and also check to make sure the lower half of the case does not get above 450. Simple process control to ensure I get the necks up to temp while not annealing anywhere near the head.
Without a high end micrscope I cannot see the crystalline grain structure to prove that I have annealed the brass. So I use empirical data. Each bullet has the same feel when seating into the case neck. Next, ES must be low for a batch of ammo. All of my brass lasts for around 12-15 reloads. Where it used to only last 5-6 with my max pressure loads before I annealed. Finally, The ammo should be capable of holding 1/4-1/3 moa anywhere between 100 and 1000 yards (or the best accuracy potential of the rifle) and not degrade in accuracy as the brass continues to get fired.
So far this method has given me very good results. High accuracy and high brass life.
