As co-owner of Ballistic Edge Mfg. I thought I might chime in here.
Ballistic Edge currently manufactures 3 different annealing machines with 2 more in the works. All products lines have been continuously upgraded and updated. All machines include forced air cooling.
Models include, the model 360. A utility type machine that operates by the timing method of annealing. The top plate will accept all rifle cases from 17 to 50 bmg as well as some larger pistol cases. As well as the top plate has been redesigned so it can have some heat sink capabilities.
Model 400 is a custom built machine designed for the competitive/long range shooter. Method of operation is constant motion method of annealing. Designed with safety in mind the top plate is a large heat sink to protect the cartridge bases. Also due to precision machining there is no wobbling of the case as it rotates and passes through the flame like other manufactures. The cases rotate on their axis as they rotate through the heating cycle.
Model 450-S is a variable speed version of the custom built model 400. It works on the same principle of annealing as the 400 and allows for the owner to adjust rotational speed to tweak amount of heating. Can be used for higher production levels as well.
One thing to keep in mind, no matter the type of machine or method of operation. Both time and more so quantity of heat have a large impact. Other factors include alloy of the brass, manufacture, processes during manufacture (ex. during the draw process when was the last annealing process and steps that took place after factory annealing and before it was loaded and sent out) whether you mix cases, physical size of the case, how much the cases is worked, thickness of the brass, quality and consistency. All contribute to the process and the outcome. Many of these are beyond the control of the reloader.
Annealing the brass case can be successfully achieved with a very large range of temperatures. Time is inversely proportional to the temp. Ex. achieving a temp of 450 deg F. will anneal the cartridge case but the time in the heat is impractical as heat propagation will damage the cartridge case head thus allowing for a catastrophic failure. Conversely higher heat of the brass, close to 900 deg. F. for very short periods of time will accomplish the task and heat propagation is lesser of an issue. Remember the temperature of the flame of a propane torch is 3623 deg F. In brass manufacturing annealing is different for the various stages in the process.
When asked how hot to get a case, I recommend from 700 to 800 deg. F. target area and to aim for 750 deg F. There are a few methods for monitoring temperature but I recommend Tempilaq as it is more repeatable and scientific than trying to achieve a certain color during the heating stage.
With a 100 degree margin, some minute details become very insignificant. Things that are further from your control are magnetic fields, electrical line current and voltage fluctuation, high frequency electricity, electrical circuit warm up periods, friction, ambient temperature, static to name a few outside variables that effect all reloading equipment.
To the common reloader there is not a real practical way to monitor hardness of the brass case. Keep careful records not only of the process but how the process effects your rifle and program, which is truly the most important thing. That is why I recommend the Tempilaq for the consistency from batch to batch. I have some customers who report they find more consistent results at 650 deg and I have some who shoot for 800 deg. Bottom line is, there is no set answer and it is just another variable you have to figure out as to what works best for your rifle, brass and reloading program.
I thought I would relate a learning moment as relayed by a customer.
The customer began extreme long range shooting and decided he wanted a machine. I built his machine. While waiting the customer bought a large lot of new expensive brass and began load work up. He received the annealing machine and used one time and found it shrunk groups. He then figured that if a little bit was good a lot would be better. He proceeded to anneal after every conceivable step in the reloading process as well as every case he bought. He annealed after trimming, annealed after de-burring, after cleaning, etc. When he finally was ready to finish he discovered the cases were so soft they collapsed during seating. All of their cases were to soft and were ruined.
Moral you can over anneal as well as there can be too much of a good thing.
Thank You
Ballistic Edge Mfg.