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Rosebud

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Not seeing much to worry about, unless you're having trouble lifting the bolt on extraction. Primers still appear to be rounded on the edges.
 
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How many times fired on the brass?
Any extraction problems?
Were all the cases showing this?
2nd firing, 1st firing it was Factory Nosler 140 accubond
No sticky extractors
Yes, these were what all the cases at the given powder weight were typically showing
 
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Not seeing much to worry about, unless you're having trouble lifting the bolt on extraction. Primers still appear to be rounded on the edges.
I was thinking the same thing about the primers "the primers aren't all that flat" but then the ejector mark started showing up -barely visible at 50 grains, slightly visible at 51, and clear and shiny at 52 grains of powder. So I thought maybe on this 280AI the primers aren't going to flatten as pressure builds (like they do on my STW for instance where they can get totally smashed before I see other signs and need to back off). Maybe that shiny ejector mark doesn't mean very much in terms of whether it is reaching an over-pressure or not, I really am not sure.
 

Rosebud

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You really can't read primers for pressure signs, unless you're seeing cratered firing pin holes. Look for heavy bolt lift and recoil that seems excessive. Back off from there. If you have a chronograph that will be a great help. If you're getting hundred fps more than you are supposed to then you'll know.
 
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Read the brass more than primers. I do a combo of everything. If I start getting flat primers I say stop, if brass shows I call it and stop. If bolt lift gets heavy I stop. That way your always safe. Thanks not thing I don’t look at is cratering because some firing pins leave them anyway.
Thanks, that makes sense.
 

gohring3006

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Check your speed.
If you’re uncertain about a given charge you can always load one case several times until your primer pocket gives out. I would probably back off if I couldn’t get 6-8 firings before it loosens up.
Have you adjusted the die for your chamber? Or are you neck sizing?
 
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Check your speed.
If you’re uncertain about a given charge you can always load one case several times until your primer pocket gives out. I would probably back off if I couldn’t get 6-8 firings before it loosens up.
Have you adjusted the die for your chamber? Or are you neck sizing?
Action only allows 3.33 OALength and so does the magazine. 3.33 is the spec length for the 280AI but this chamber is longer. I've been seating at 3.33 so it's way off the lands about .040 (measuring from a black-marker dummy bullet set to touching the lands).
 

gohring3006

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Action only allows 3.33 OALength and so does the magazine. 3.33 is the spec length for the 280AI but this chamber is longer. I've been seating at 3.33 so it's way off the lands about .040 (measuring from a black-marker dummy bullet set to touching the lands).
I’m sorry, I was referring to your sizing die.
Sometimes if the shoulder is bumped too far, you can give the case a little running start to slam into the bolt face, and if it is a little rough around the ejector hole it can give a false positive.
 

Bob Wright

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Sticky bolt, and brass swipes definitely tell you there is impending doom. If you ran a 10 shot ladder it would normally happen progressively. Nosler brass does not handle high end loads. Therefore I won't shoot them on the upper end and drop down to the next lower node. I don't see anything too concerning on these pictures, but the primer pocket growth will be more apparent. I check mine with pin gages when I start seeing minor brass swipes.
 

TRexF16

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Just curious but do you have access to any pressure-tested data for IMR 4166 in the 280 AI? The closest cartridge I could find with a quick look was the 270 Win and their 64K PSI loads were far below yours for both the 140 and 150 grain charges. Obviously the 280 AI would use bigger charges than the 270 Win for two reasons - slightly greater bullet diameter, and slightly greater case capacity. I know 4166 is supposed to be kind of a substitute for VARGET but that does not necessarily relate to charges, but published max charges for VARGET in the 280 AI is a lot lower too.
Do you have velocities for these loads? That's probably a much more reliable indication of pressure than any visible signs. I would look at the velocities Hodgdon got with VARGET with 140 and 150 grain bullets at max pressure in the .280 AI (2903 FPS for the 140 and 2750 to 2800 for the 150, depending on the bullet) and not trespass above that.
I would figure 4166 a bit on the too fast side for the bullet weight you're using. That said, 2900 FPS with the 143 Hammer will sure kill fine.

Just my two bit first impressions and questions,
Cheers,
Rex
 
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Reelamin

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To each their own, but I would be throwing more powder in it based on the photos and comments of the OP.
 

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