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Annealing opening up groups?

But if you size with a bushing spring back reduces neck tension.

If you size with a mandrel or expander ball spring back raises neck tension

As the brass work hardens this effect is more pronounced. Annealing every firing makes the spring back effect consistent instead of changing with every reloading cycle.

I get your point now. I need to do some measurements after bushing sizing. For small dimension changes the spring back may be negible. Need to check this out and get some real numbers. True tension/grip is more complicated than just the neck diameter change after inserting a bullet. Actual hardness and dimension change. My Redding FL non bushing die closes the necks down way to much. The bullet expands the neck about 6 thou. You can control the diameter change better with a bushing die or a custom die made to match fired cases. I agree now with your comment.
 
Yep, sped up from 2820, to 2870.

Ultimately dropping the powder charge slightly, and moving seating depth brought the groups back.

I've put a few hundred more rounds through the rifle, and have started annealing every firing; it's back to being consistent. ES/SDs were improved when I ran it over the chrony this weekend, but I also started using an FX120i, so unsure if that's attributable to the powder or annealing.

I'm pretty sure it's a combination of both, in any event glad you got things figured out. Some time our accuracy issues create a thread that can be extremely interesting as well as enlightening, thanks for both.
 
I get your point now. I need to do some measurements after bushing sizing. For small dimension changes the spring back may be negible. Need to check this out and get some real numbers. True tension/grip is more complicated than just the neck diameter change after inserting a bullet. Actual hardness and dimension change. My Redding FL non bushing die closes the necks down way to much. The bullet expands the neck about 6 thou. You can control the diameter change better with a bushing die or a custom die made to match fired cases. I agree now with your comment.

I do things many different ways.

For my 6br bench gun i use a harrells simi-custom bushing die. Then k&m expander mandrel for final neck sizing. Works great. Gun shoots in the 1's and 2's.

I have also had great results with the whidden full length sizer with his expander ball kit to fine tune neck tension. Runout.with it is almost.nil.

I have forster full length sizers that have been honed. I like the whidden but if you are.going to use the expander ball forster has.got it dialed.

I just don't see why everyone has decided a full length die with expander is so bad. In my opinion other than controlling neck tension, which whiddens expander ball kit has addressed, bushing dies bring on more problems than they solve.
 
...True tension/grip is more complicated than just the neck diameter change after inserting a bullet. Actual hardness and dimension change.

Exactly.

Using too-small a FL die neck dia., then pulling an expander ball back thru too-small case neck does things to brass that’s more long-lasting in its effects on what we refer to as neck tension than minimally sizing necks down, either with a honed FL die or with a neck bushing of suitable ID.

The additional step of using a sizing mandrel in either instance, instead of an expander ball in the first or after neck sizing with a bushing in the second, will have different effects on what neck tension results. I personally prefer the latter practice.

Annealing is of benefit in both instances but it’s not a cure-all. Best practice - in my opinion - is to move brass as little as possible during sizing operations.
 
Exactly.

Using too-small a FL die neck dia., then pulling an expander ball back thru too-small case neck does things to brass that’s more long-lasting in its effects on what we refer to as neck tension than minimally sizing necks down, either with a honed FL die or with a neck bushing of suitable ID.

The additional step of using a sizing mandrel in either instance, instead of an expander ball in the first or after neck sizing with a bushing in the second, will have different effects on what neck tension results. I personally prefer the latter practice.

Annealing is of benefit in both instances but it’s not a cure-all. Best practice - in my opinion - is to move brass as little as possible during sizing operations.

No doubt a custom full length sizing die made from your fired brass is the best possible solution. Very little brass movement here. Probably why many short.range benchrest shooters never anneal their brass and have the results they do.
 
Hey Guys,

I picked up an AMP last week and annealed some cases for a rifle that historically has shot very well, and very consistent. When I took it out to the range today, I shot some leftover match ammo that hadn't yet been annealed along with some annealed rounds I just loaded up; load data/everything identical except the cases.

The newly loaded rounds had their groups open up noticeably at 300 yards vs. the rounds I'd loaded up earlier. I also "Aztec'ed" another round just to make sure I didn't over-anneal the cases previously.

That said, I'm curious if you guys have run into this before? I'm thinking of dropping down .001 in bushing and testing again, but wanted to see if anyone else had any thoughts as to what happened.

For reference, this is a 6.5, and I'm running Alpha LRP brass. The cases I previously annealed were done using aztec code 152, and the machine just analyzed another piece of brass at 153...so I'm thinking I didn't over-anneal anything.

Thoughts?
Just read your first post and not going to read the whole thread. On the AMP web site they tell us annealed brass does not spring back. If you want the same sized neck as you had with the unannealed brass, you have to use the next size up in bushings, not .001 smaller.
 
Do you size your brass before or after annealing. I always size after I anneal and have found that there is more consistent neck tension when doing it this way.
 

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