Extreme Reloading (retooled): Annealing, Expanding, Turning, and Trimming

[@neilharris4462]

A neck sizing mandrel, in my opinion, eliminates the need for neck turning unless using a tight necked chamber. Using quality brass with a .002 undersized mandrel (.306" for 308win) is about where you want to be.

[@sdkweber]

I am working in that same direction and have continued neck tension testing. It still looks like 0.002-0.0025" of "tension" is best in my RPR. I have shot groups now using a neck sizing mandrel down to 0.3065". I have a 0.3060" mandrel and am planning to load and test some rounds using this next. Thanks for watching and posting!

[@jackboshoven8316]

One thing you may want to consider in your further study of annealing is the impact of time on achieving a full anneal at a given temperature. The 750 degrees Fahrenheit that you are annealing too requires 1 hour at that temperature to achieve a full anneal. The problem with brass is that in order to achieve a full anneal at these temperatures does not work because if you heated the neck to 750 degrees Fahrenheit for 1 hour you would obviously ruin the case because the base would also reach that temperature. In order to anneal the neck, but not anneal the base, you have to flash anneal. Flash annealing takes higher temperatures. During annealing the brass goes through essentiality three "regions" as a function of time at a given temperature. The first bit of time is "recovery" where the hardness stays pretty much the same, but does not decrease. The next region is where recrystallization of the metal takes place, during which the hardness is reducing at a fairly fast rate (do not want to be here because small changes in time result in large changes in hardness differences). Once past recrystallization then grain growth begins where the hardness stays pretty level and you achieve the full anneal (region you want to be in). In order to not anneal the base of the case, one has to flash anneal the mouth (where annealing times are on the order of seconds so that the base of the case does not have time to heat up and begin to loose strength). To flash anneal the brass has to be heated to higher temperatures closer to 950 degrees Fahrenheit to get past recrystallization and to grain growth within the few seconds that you can apply heat to the mouth without heating the base. Brass begins to glow orange at about 950 to 1025 degrees Fahrenheit, which is still well below the melting point. The fact that heating the brass is a transient event, you cannot get the brass instantaneously to 950 and hold it for 5 seconds (assuming that is the temp that gets you to full anneal in that time) Therefore one has to play around a bit with the time in propane flame to get the right temperatures for long enough to reach a full anneal. This will depend on the exact Cu/Zinc composition of the brass and the mass of the neck you are heating. As most of us do not have hardness testing capabilities in our shops, we are left with shooting the annealed brass and playing with the temp/time (while making sure we do not heat the base of the case) until we get the consistency we seek. To make things more complicated, the temp/time will be different between the different alloys brass manufactures use and the mass of the brass in the neck region (again different between manufactures and cartridge type).

[@sdkweber]

Hello Jack and thank you for watching and posting this information. The time component certainly complicates things and I really did not read anything about this on many of the websites and papers I read about annealing. It makes sense that to achieve the change (softening) we are looking for that it might take time at the temperature normally used. Is the process you are describing used by the AMP system?

[@jackboshoven8316]

The AMP research that I have read alludes to this but I did not find any direct mention in their stuff. I am not a metallurgist by any stretch of the imagination, but I do remember my metallurgy class thirty years ago and the discussions around the impact of time on annealing and the stages one goes through. A quick Google for brass annealing and the 370 Celsius for 30% zinc shows that it takes 30 minutes to get to a full anneal.

[@sdkweber]

@@jackboshoven8316 Thank you Jack. I will continue to read up on this!

[@josephhomen]

This echoes exactly what I’ve heard from metallurgist

[@josephhomen]

The Reese on the range channel has some very good info on this exact subject. He is also a metallurgist and shooter/reloader. m.kzbin.info/door/0EOdvRUpYpVoVnSdFXFXFg

[@BBouncer]

I've run into the same exact issue when turning necks for a factory chamber...my solution has been to only "clean up" high spots on the brass for my precision builds, or simply not turn at all if using good brass (Lapua or Alpha).

[@sdkweber]

Right on BBouncer5150. Premium brass is worth it and if you are interested, we did a video on Alpha Munitions brass. Here is the link: kzbin.info/www/bejne/pnulgIiXaNJneac We have a follow up on that coming out this summer. Thanks for watching and posting.