Flame Annealing - almost perfect

[Straightshooter1]

Finally got together with my shooting buddy who has an AMP annealer to test what my hardness tester shows after a case has been anneal with the AMP. As a reminder, my goal is to have my cases at the same hardness when finished with sizing as the hardness of my virgin Lapua cases (as reading on this tool of 15). So, we took a case and sacrificed it to get the AMP's code, per AMP's instructions. Set the code and annealed 3 cases. Cleaned off the oxidation layer with some steel wool, ran a bore brush through the necks too and then measured the hardness. As I suspected, the hardness showed all three of them being right at 15. Great, huh? The problem is, we now have to size the cases, which will increase the hardness to 17 on this tool.

I guess 17 is not necessarily "bad", especially if it's consistent. My old flame annealing approach where I'd just drop the case out of the flame when the flame started to turn orange would essentially get me the same results (17 after the sizing process). To get my necks to the 15 hardness reading I have to anneal them to where I get a 13 reading and the sizing bring them back up to my target of 15.

Apparently, if one is using a AMP machine, one will have to customize a code to anneal the cases more than the code that's produced so that the sizing brings the hardness to that 15 reading I get on virgin Lapua brass.

Just thought I'd share this to show what the AMP machine is going in comparison to what I've been doing with my flame annealing process.

 

[Killick]

Not certain if anyone has raised this issue but when you buy virgin brass you still size it to get the neck to your specifications so I would think annealing it below “15” is superfluous.

 

[Webster]

Finally got together with my shooting buddy who has an AMP annealer to test what my hardness tester shows after a case has been anneal with the AMP. As a reminder, my goal is to have my cases at the same hardness when finished with sizing as the hardness of my virgin Lapua cases (as reading on this tool of 15). So, we took a case and sacrificed it to get the AMP's code, per AMP's instructions. Set the code and annealed 3 cases. Cleaned off the oxidation layer with some steel wool, ran a bore brush through the necks too and then measured the hardness. As I suspected, the hardness showed all three of them being right at 15. Great, huh? The problem is, we now have to size the cases, which will increase the hardness to 17 on this tool.

I guess 17 is not necessarily "bad", especially if it's consistent. My old flame annealing approach where I'd just drop the case out of the flame when the flame started to turn orange would essentially get me the same results (17 after the sizing process). To get my necks to the 15 hardness reading I have to anneal them to where I get a 13 reading and the sizing bring them back up to my target of 15.

Apparently, if one is using a AMP machine, one will have to customize a code to anneal the cases more than the code that's produced so that the sizing brings the hardness to that 15 reading I get on virgin Lapua brass.

Just thought I'd share this to show what the AMP machine is going in comparison to what I've been doing with my flame annealing process.

Is there any data to relate Webster units to ASTM hardness units. Unfortunately there is no std ASTM unit to report hardness to. I would like to get an idea of what a spread of 15-17 relates to in HRB scale. Is it a trivial amount?

 

[Straightshooter1]

Is there any data to relate Webster units to ASTM hardness units. Unfortunately there is no std ASTM unit to report hardness to. I would like to get an idea of what a spread of 15-17 relates to in HRB scale. Is it a trivial amount?

The tool I have came with a manual having a conversion table, which I think helps provide an idea of what those increments represent:

 

[Straightshooter1]

Not certain if anyone has raised this issue but when you buy virgin brass you still size it to get the neck to your specifications so I would think annealing it below “15” is superfluous.

How much one might work the brass will effect the amount of change in hardness. I for one, and I've heard many others too) don't size their virgin brass. It's not a typical thing to do, is it?

Because my Lapua brass has come packed as bulk in a blue box where some mouths are dented, I will run a mandrel through the all the cases in the box to be sure the necks are rid of any dents or out of roundness. I can tell you that doing so does not produce additional hardness that I can detect with this tool. But certainly if one is sizing the virgin neck down and expanding it back to a desired neck tension, then that hardness will definitely increase measurably. In fact, when I take a virgin .308 Lapua case and seat a bullet well into the neck, then pull it and measure the hardness, it goes from 15 to just shy of 16 (I estimate it at ~15.75).

Regarding annealing with an AMP, I meant to mention that there is another approach to keeping the result at the virgin brass hardness. That would be to do all the sizing process before annealing with the AMP. Then you'll get the same hardness as the virgin brass.