AMP Aztec codes evolving over life of brass?

[MikeMcCasland]

Hey Guys,

I have some 6mmGT brass I'm prepping after shooting a match earlier today. During this brass prep session I randomly decided to reanalyze a piece of fired brass because the code I'd generated after the first firing (131) seemed lower than I would normally expect.

The new code read out at 143. I decided to sacrifice another case, and it came out 144.

I'm planning to anneal this batch of brass at 143 going forward, but I'm curious what I should make of this?

The first code I received from the machine came after the brass had been neck turned, and once fired. I weighed cases and Aztec'ed a turned/fired case per the instruction. This is basically my process for all my brass, and really haven't thought twice about it until now.

If you're using bushing dies, and AMP annealing, are yall reanalyzing brass after several firing/sizing cycles (i.e. once the unsized portion of the neck has had a chance to thicken up)?

Thanks,
Mike


Edit: I should add, this brass hasn't been shot a lot. Maybe 3-4 firings at most.

 

[Shooter13]

I have thought of this also but never had re-analyzed it, may have to see what it does as I have some brass that has several firing on it. If I do it in the next few days I'll let you know.

 

[Dusty Stevens]

I wonder what it would show if you just reanalyzed a piece from a box that had never been shot like just put it to the side for 6mo. Btw youll get number swings that far away out of the same box as new

 

[Kraven]

I reanalyzed some brass after several firing and it came out within +\- .001 from a brand new one. Negligible difference. Probably a good idea to warm up the heating element when it gets real cold.

 

[Jdne5b]

I reanalyzed some brass after several firing and it came out within +\- .001 from a brand new one. Negligible difference. Probably a good idea to warm up the heating element when it gets real cold.

What about the ambient temp of the brass you're testing?

 

[MikeMcCasland]

I wonder what it would show if you just reanalyzed a piece from a box that had never been shot like just put it to the side for 6mo. Btw youll get number swings that far away out of the same box as new

I never analyze new brass; I think you're only supposed to aztec once fired for your code.

I usually don't get much variation (I've nuked a good bit of brass), but I suppose unturned new brass might show some.

Most of my stuff gives codes within 1-2 of each other.

 

[Retired Grunt]

Peterson has a Spreadsheet to Download and you can look up the code by Lot #. My first batch wasn't listed, so I ran the Aztec and showed 136, I just bought 100 more for new cases for next year and the spreadsheet shows 144. I haven't shot them yet. So I guess I will reanalyze the old ones.

 

[Bob L.]

OP,
I noticed the same thing with 6 BRX brass. I don’t know what to make of it either. I’ve decided to keep using the latest Aztec code (fire-formed, neck turned brass).

 

[Dave Way]

On a slightly different note, I also have an AMP with Aztec mode. I had four sets of 6BRA brass that had been fired nine times and never annealed. After firing 7 to 8 times, neck tension became lighter. I had to start playing with tighter bushings due to spring back.

I tested one of these cases and came up with the recommended Aztec setting of 153. I annealed a case and tested neck tension, actually seating pressure, with a 21st century hydro seater. It had not changed. I worked my way up to 160 when I was finally able to see spring back decrease, but not to the point it needed to. I ran the case again at 160, and the brass was right back where it shot well in the past. I then ran all 200 cases through twice at 160, allowing them to cool down in between. Since then, I’ve been running at 160 after firing and neck tension is extremely consistent. I’ve shot smaller groups at 1K than ever with cases that now have 13 firings on them.

I consider Aztec mode a guide but prefer to verify its accuracy in terms of spring back or should I say the lack of spring back.

Dave.

 

[INTJ]

This is interesting, but I guess it's what we'd expect. In @MikeMcCasland's case, it seems that Aztec mode doesn't completely anneal each time. Maybe the thought is (from AMP) is that slightly under annealing is preferable to over annealing.

In @Dave Way's case, it shows that work hardened cases need more annealing, aim it seems like the Aztec analysis is recommending a slight under annealing.

What does AMP say about his?

 

[Mikemci]

Maybe Alex will chime in ?
I'm not even sure if he monitors threads here.

 

[MikeMcCasland]

This is interesting, but I guess it's what we'd expect. In @MikeMcCasland's case, it seems that Aztec mode doesn't completely anneal each time. Maybe the thought is (from AMP) is that slightly under annealing is preferable to over annealing.

In @Dave Way's case, it shows that work hardened cases need more annealing, aim it seems like the Aztec analysis is recommending a slight under annealing.

What does AMP say about his?

I emailed Alex; I don't think he understood my initial question.

I had provided some detail about what I was doing so he had some context, and I think he kinda latched on to the 6mm GT aspect; he replied back explaining how they went from a pilot code of 73B to 73C as factory 6mmGT brass became available.

That said, my question doesn't really pertain to any specific caliber.

Basically....is there a need to re-aztec for a new code after multiple firings with bushing die usage. We know the necks are going to thicken in the sections that aren't sized by the bushing; this would seemingly mean that you'd need to re-analyze, but figure we'll let the expert chime in.

I simplified the question, and replied to him. We'll see what he says.

I'm probably going to nuke some 308 Palma brass that's been fired a ton to see what it does.

Thanks,
Mike

 

[MikeMcCasland]

Not sure what to make of this; I'm 99.9% sure I used 73C for both.

I guess I'll try it again on a new batch I'm about to turn.

Mike Email1:


Hey AMP,

I’ve got some 6mmGT brass that I neck turned when new, fired one time, and then AZTEC’ed to obtain the code of 131.

Since it’s first Aztec’ing, I’ve put another 1-2 firings on the brass, and annealed each time with the 131 code. I’m sizing with a bushing die for reference.

This now puts me at firing ~2-3 on these cases.

Today I took the cases and randomly AZTEC’ed two of them; this time obtaining the code of 143 & 144.

It’s my plan to anneal this batch of brass with the 143-code going forward, however I’m curious why the code would have grown so much (I assume from brass build-up in the unsized portion of the case neck)? If so, is this expected behavior (i.e. should I be re-aztec’ing pieces of brass after a few firings if I do this same procedure for other calibers).?

I’d be curious to get your thoughts/feedback on the matter.

AMP Response 1:

"Hi Mike,



Thanks for your email. The first samples of GAP 6 GT we received several years ago were formed from 6.5 x 47 Lapua, with the necks then turned to 0.012”. This was when it was still a fairly obscure wildcat, and well before factory brass came available.



Those sample cases had much thicker shoulder/body dimensions compared to the turned neck. The AZTEC code we settled on worked perfectly for that wildcat brass. George Gardner, the developer of the cartridge, recently sent me samples of Alpha GAP 6 GT brass and two lots of Hornady brass to test.



The results we got showed that our listed AZTEC pilot/analyse code 073 B gave annealing codes which under-annealed the factory cases by a considerable margin. The factory manufactured cases have much more consistent case walls from neck through to the body. We had to change the value of the suffix letter to get the correct annealing result. I have added a new AZTEC pilot code 073 C to our listings for the factory cases. https://www.ampannealing.com/aztec-settings/ You will see that directly below the listing for 6.5 x 47 formed cases. I believe that George Gardner posted the news on his Facebook and website.



We have retained the original 073 B listing for those reloaders who still form from 6.5 x 47 Lapua, and we have distinguished between the two in our AZTEC listings.



Regards"

Mike Email 2 (Clarification)

Hey Alex,

This is factory Alpha brass, and each time I AZTEC’ed the brass I used 73 C as the analyze code.

I guess the caliber doesn’t really factor into the question; do I need to re-aztec brass after a few firings if I’m using a bushing die? i.e. will the growth in the unsized portion of the neck result in the need to further anneal after multiple firings on brass.

Thanks,
Mike

AMP Email 2:

Hi Mike,



No, multiple firings will not account for that discrepancy. If anything, over time the neck and shoulder can get slightly thinner, and require a slightly lower annealing code. This usually just applies to reloading for semi-autos, which require a larger shoulder bump when full length resizing.



I’m not sure when you first analysed your cases, but 073 C was first calibrated in March 2020. Prior to that, only 073 B was listed for GAP 6 GT. The difference in values between B and C is 12, so if 073 B was used on Alpha brass you would get 0131, and the same brass would give 0143 using 073 C. Those are exactly the same numbers we generated on the samples we received from George Gardner.



Regards



Alex

 

[LVLAaron]

I've re-tested stuff after many firings and came up with the same number +/- 1.

 

[Chuckhunter]

I've re-tested stuff after many firings and came up with the same number +/- 1.

Have gotten the same results as Aaron, after approx. 5 or 6 firings, I run then back over the neck turner some take a tiny amount off and some don't take any off but usually after the second turning the growth pretty much comes to a standstill. I do anneal between each firing and codes have never changed more than +/- 1

 

[INTJ]

After six firings I burned a case to check the Aztec code. The code for once fired cases was 148, after six firings the code is now 150. I had also noticed that seating pressure had slightly increased after the fifth firing. The new code seems to have resolved that. 6 BRA, annealed after each firing.

Makes me think that the Aztec code is very slightly on the under annealing side.

 

[dgeesaman]

After six firings I burned a case to check the Aztec code. The code for once fired cases was 148, after six firings the code is now 150. I had also noticed that seating pressure had slightly increased after the fifth firing. The new code seems to have resolved that. 6 BRA, annealed after each firing.

Makes me think that the Aztec code is very slightly on the under annealing side.

I’ve reanalyzed (burned) a case from a batch after some firings and I usually don’t get the same results. I’ve also analyzed three from the same unfired batch and seen the code vary by 2-3 points. So I haven’t worried about a single code point at all.

 

[Joe Salt]

I shot a match last year that cost me a win, the eighth shot went low out of the group. I number my cases so I know which cases to check. My analyzed brass Lapua 6mm Dasher was at 134. well number eight had blow by down to the shoulder. So next match after talking to a buddy told me to go to 137, which got me a 5.1 inch group and the win. So I'm now keeping an eye on my fired cases. I believe your better off tweaking it make more scents.

Joe Salt

 

[bwoodie]

I asked Alex Findlay this question earlier this year:

I have been analyzing brass after it is “once fired”. Do I need to repeat the analysis again after the brass has been fired 2x, 3x, etc or is the original code appropriate to keep using?

and his response was:

"Analysis should always be done on a fireformed, unsized case. Once you generate that number, it is good for all subsequent reloads. The only exception would be if you are using a semi-auto rifle, which requires aggressive full length sizing. The combination of sizing and trimming means that enough brass is lost at the front end of the case to thin the neck and shoulder. After around five reloads it is wise to sacrifice another case, which will usually give a lower number."

 

[INTJ]

I asked Alex Findlay this question earlier this year:

I have been analyzing brass after it is “once fired”. Do I need to repeat the analysis again after the brass has been fired 2x, 3x, etc or is the original code appropriate to keep using?

and his response was:

"Analysis should always be done on a fireformed, unsized case. Once you generate that number, it is good for all subsequent reloads. The only exception would be if you are using a semi-auto rifle, which requires aggressive full length sizing. The combination of sizing and trimming means that enough brass is lost at the front end of the case to thin the neck and shoulder. After around five reloads it is wise to sacrifice another case, which will usually give a lower number."

Well, I don't think that is right in all situations. After five firings and annealings, my seating pressure was increasing. The most likely cause of that would be brass work hardening, meaning it was being slightly under annealed. That's is why I reanalyzed.