280 Ackley Question

BadgeNJ

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I have a 280 Ackley and noticed when FL sizing brass that the bottom of the case took a lot of effort to get through the die. When the gun was chambered I sent FL sized cases and the Redding dies to the gunsmith (SAAMII Dies). I took a fired case marked 4 spots bottom of the case 1/4, 1/2 and just before the shoulder:
Fired case bottom up .475 - .467 - .460 - .455
FL sized case bottom up .470 - .463 - .457 - .452

Is this an issue?? I did the same with my factory 308 and did not see as much of a difference between the cases.
 

Badlands Griz

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My 280ai program is the same way. Other than having to put more pressure on the press handle than I'd like, I haven't seen any detrimental effects.
I try for a .002 shoulder bump. Measuring diameter of fired vs diameter of sized, with the greatest variance being .005 at the base of the case, this gives a sized cartridge clearance of approximately .0025 per side (or .0025 around the circumference). This seems not only tolerable, but optimum for a setup that I use in the field.

I would be interested to hear if anyone has differing information. I'm always looking to learn.
 

MagMan

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My fired base and FL both measure .469”
Measurements at the .240” line are .472” fired and .469” FL sized.

Shoulder fired are .456” sized are .452”
 

dok7mm

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I also used Redding comp dies on my son's 280a.i. with similar results.

The relationship between chamber and die is excessive and you end up sizing too much. It likely over works the brass, leading to a lot of trimming after a few firings. Then the shoulder moves into the neck and you end up creating a donut.

On my son's rifle, the donut arrived on some 2x fired and all on 3rd firing. I used mandrels to force the donut to the outside and turned necks + a bit more in the shoulder. I used pin gauges and tubing mic to verify all was well. It took a lot of time and was a PITA.

I knew it would happen again down the line, so I shopped for new brass and bought a sizer from Forester and Hornady. Returned the Forester and kept the Hornady, as it sized the shoulder only .002" and .0025" above the web. Turned the necks and everything worked out fine, some are on 5th firing and very little trim has been needed & no donuts.

Just my experience!
 

BadgeNJ

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Other than the difference between the chamber and the die in the body of the case, so far the head space difference between fired and FL sized bumbs back the shoulder .001 to .0015. Just was not sure if the chamber die difference would be a problem with the brass. I hope I am understanding this correctly and thanks for the replies. This stuff get crazy sometimes.
 

dok7mm

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It is the diameter of the case you are compressing. That brass has to go somewhere when your die is a good bit tighter than your chamber, only place is into the neck length.

If you know what your chamber neck length is and your trim length, you should see if the neck is moving forward excessively with each firing. That is an indicator of what I described above.

Softer brass, higher velocities and a tight die/looser chamber all contribute to this, if I'm correct. OR, you might change your lube!
 

GatorTrapper

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Buy a Redding neck sizing bushing die and shoulder bump die.
No need FL size the cases in a bolt gun that has a round chamber.
 

lancetkenyon

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Buy a Redding neck sizing bushing die and shoulder bump die.
No need FL size the cases in a bolt gun that has a round chamber.
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Tiny Tim

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I can't speak as to whether your chamber is a bit oversize, but it seems you are overworking your brass and that is causing additional issues, i.e. cases growing, doughnuts forming, possible reduced case life. If the cases will easily rechamber after firing, perhaps a custom honed die would help, although if chamber is on the max size or over, the die would only be good for this chamber.
 

nksmfamjp

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I will check with Redding on a custom die or should I look at other sources
Have you asked them if they can hone it out and get you maybe 1-2 thousandths? Might get you going. Also, I wonder if a chamber cast would reveal an oversized chamber.....Whidden, Redding or Hornady shoul be able to set you up with a custom die.
 
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