• The Realities of Case Annealing

    Case annealing has come up more than a few times on our reloading forum, and even just recently we have had two or three threads dedicated to the topic. While many shooters prefer to just `load and shoot`, or better yet ‘buy and shoot`, for the precision reloader annealing their brass is very much a part of the reloading process.

    But is the extra effort really worth it? Does annealing really result in more consistent neck tension? That and other questions regarding the subject are what lead the manufacturer of the Annealing Made Perfect Induction Annealing Machine to conduct scientific testing with accredited laboratories to either validate or disprove their beliefs and theories on the subject. They then worked with Bill Gravatt and Mic McPherson to compile the data and put together the following technical write-up on their recent research and testing. In their own words:

    "We decided it was time to revisit the metallurgy of what we do to find the empirical evidence (if any) of the benefits of correct cartridge case neck and shoulder annealing. Specifically, is our annealing absolutely repeatable and consistent, and if so, does that result in more consistent “neck tension” for our customers?”
    The full technical report can be found on AMP's website using this link: Annealing Under the Microscope

    Comments 4 Comments
    1. JASmith's Avatar
      JASmith -
      Excellent discussion!

      The effect of carbon build up on pull force is rather interesting.

      Did I overlok the control tests? In particular, the variation of pull force between cases and from shot to shot when no annealing is done?
    1. RC20's Avatar
      RC20 -
      There has been an extensive discussion on this over the The Firing Line reloading site.

      While complex, it also has been done with a healthy degree of scientific testing and end results.


      One aspect that I have been most interested in was a fellow called Jeep Hammer and another Supercub 99 found that inductive annealing was significantly affected by clean and carboned cases. Clean took longer.

      While AMP contribute discuss this, they do not say that they have a program for it or the use of one of the programs that achieves the "perfect anneal"

      While good, it will under anneal and therefore is not perfect. Same brass but different dates and lots will change. So I am not in agreement with perfect. I think a tad under annealed is better by far than perfect or going over when perfect is not, which does ruin the brass for spring back.

      There is also the aspect of cross comparison using Hardness as the control factor. While that is probably fine for a given batch, the in depth assessment is what is accurate.

      I also question the carbon issue, when I have done my Annealign using Annie and Templilaq (see below) I got cooked carbon and hard seating without a lube (first round, next are fine)

      So another aspect of this is should the case be cleaned with Steel Pins and solution to get perfectly clean (I think its a good idea but equipment cost has me short of that yet)

      Supriecub 99 also came up with the perfect answer to the wet cases, cheap food dryer from Wallmart works perfectly.

      Then there is my experience with my testing method of Templiaq (which is the same as torches use)


      In short this is not ever going to be perfect, it takes serious attention and AMP if it does off you will not know it until you shoot the brass.

      I am for under annealing deliberately as not to go over and I am not after perfect.

      There is good enough (a tad under) and then there is the iffy statement of perfect with so many variables and no feedback mechanism to see that.
    1. JASmith's Avatar
      JASmith -
      I full length size after annealing.

      This puts some work hardening back into the brass. I think the step also makes the yield strength more consistent because strain hardening is fastest at the beginning and tapers off. That means that the spread of yield strengths is reduced.

      The strain hardening curve might also explain why some folks report better accuracy with cases that have been fired one or more times. I report "some" folks because my shooting skills aren't in their ballpark!
    1. Blitzfike's Avatar
      Blitzfike -
      The additional carbon inside a dirty case provides a material that reacts to the electromagnetic field of the induction coil. More carbon to get hot from being in the induction field, more heat to the brass case.