Got an AMP V2 machine with Aztec mode some 9 months ago. Happy (enough) with it and planning to keep it.
I was hoping the AMP machine would help improve accuracy, and that group size might reduce, from 0.35” to hopefully something like 0.25”. That did not happen. It seems that after switching to good brass, a good milligram scale, and a good die set, there are no more silver bullets left... Now it is all tiny incremental improvements, with diminishing returns.
I try to approach these things in a scientific way, so i run experiments, measure everything i can and record the data in my notebook. AMP gave mixed results, i guess not surprising, as all reloading equipment have their own pros and cons.
Pros:
1) Annealing time is quite fast, around 3-5 seconds per case. [I have not set up the case feeder yet. Not yet doing any bulk processing.]
2) Consistent annealing IF your neck thickness is fairly constant from case to case. This is generally true for premium brass with unturned necks with a fairly narrow weight range (2-3 grains delta). [Experiment: Take 20 pieces of cheap less-than-ideal brass from the same batch of factory hunting ammo, and run all of them though Aztec mode. Not all cases will show the same code... especially if case weight is very different. Results will probably be a little more consistent if you neck turn, but i have not tried it yet, and frankly neck turning cannot turn poor quality brass into premium brass. And i am also not suggesting that neck turning is required, just pointing out that small (or large) “errors” in manufacturing will propagate into post annealing material hardness and neck tension differences. Probably too small to worry about if you buy good quality brass, but good to be aware of it.]
3) Inert when turned off. Generally quite safe, just don’t touch the hot brass.
4) Fast Setup Time: Melt one case in Aztec mode and write down the setting, re-use that same setting next time. [This is a destructive test, one case is lost per batch. Always make me cringe, but yes it works. ?]
5) Shoulder setback is more consistent, and your FL die will need adjustment the first time if you switch from gas annealing to the AMP annealer, or change the shell holder (Redding shellholder set). Shoulders are softer, with less springback, and shoulder setback becomes more consistent.
6) Neck tension is a little more consistent IF you brush or tumble the cases post annealing. The AMP machine changes the surface finish of the necks on the outside and inside of the cases: Different texture, sticky to the touch, compared to the rest of the case, with a much higher coefficient of friction. [Checked this with the K&M arbor press with seating force measurement: Picked a bushing that should give about 0.002” “neck tension”. Seating force was around on average 160 lbs, which is very high, with large variation (110 to 190 lbs). Bullets seated with a loud thunk - a bit too violent. Post tumbling seating force came down to 60 lbs (almost 3x less), and range was narrower (53 to 74 lbs), so much lower and much more consistent actual bullet grip. [My best guess/conjecture: Might be the side effect of intense localized heating of the neck outer surface, which appears to oxidize. I get far more consistent seating force (and now butter smooth seating feel, with no sudden thunk), if i tumble for 3 plus hours post annealing step. Yes: Enough carbon remains in the case necks, but i use Imperial dry lube as well.]
Disadvantages:
1) Too expensive, should really cost closer to $500 if they want to achieve mass market success.
2) I did not see any improvement in SD (was already low, 7-9 fps) or group size (0.3 to 0.5” at 100) whether i anneal or not. Yes the seating force changes quite a lot if you don’t anneal for two reloads or more (2x higher), but it seems if you are in the middle of a nice wide node, even if speed goes up a little, that (at least in my case) it does not seem to matter that much. And positive compensation is always available to minimize the impact of speed changes to a degree. Of course YMMV! [I expect folks who don't do load development (who don’t try to exploit positive compensation) might actually see an improvement in SD.]
3) Might be different for others, and maybe it is the humid Gulf Coast climate rusting up my brass, but i have to tumble post annealing to get good consistency in seating force. [Perhaps try this experiment for yourself: Anneal a whole batch of 50, then tumble half the batch and keep half the batch intact, and observe how seating force and accuracy varies, if any. Honesty i really am keen to hear if you observed the same change.]
4) Aztec mode destroys one case per batch. Not the end of the world, but still....
5) Have burned myself once already, due to stupidity, and got a nice blister from it. Cases take a while to cool down, just use a tin foil baking tray (but no need to dunk them in water).
Others have mentioned the Bryan Litz experiment where he wrote up the effect of annealing every time vs not annealing at all vs annealing every few reloads, and yes there was no real difference. My own results are also inconclusive.
However, the Applied Ballistics team cleaned the barrel between each experiment and IMHO they did not fire enough fouling shots (two, i think), so perhaps a bit of a flawed experiment. Not meaning to throw rocks, they do good work for the community. [Would be great If they could repeat the experiment with a dirty barrel with at least 100 rounds through it, without cleaning it between experiments.]
Brass life: My 6.5 CM Lapua SRP brass fails after 25 plus reloads, when the primer pockets open up. I am a little worried about neck splits if i completely stop annealing my Lapua brass, so for me that is enough reason to keep doing it every three reloads. [Btw: Hornady LRP brass fails after 5-7 reloads, also due to primer pockets, and not convinced annealing is needed for the Hornady plinking ammo.]
In summary: I am keeping mine, mostly for productivity reasons and convenience. Annealing in my mind is a necessary evil to extend brass life, so it helps if it can be done quickly.
