Questions on Fire Forming 280 AI brass

I have a Kimber 84L in 280 AI inbound and was wondering about the advisability of using IMR 4831 and Sierra 120 or Speer 160 grain bullets to fire form some Hornady 280 Rem brass?

My gut says that IMR 4831 is too slow for optimum fire forming, but I hate to miss an opportunity to use some old components (powder and bullets) that I been trying to find a good / productive use for.

If I don't use the IMR 4831 or Sierra bullets for fire forming, than I am planning on purchasing some AI brass. Again, I'm trying to use up materials sitting around collecting dust.

If this is a suitable combo and I get a good crush fit on the brass, such that I don't need to jamb bullets into the lands, would 52-54 grains of IMR 4831 with the 120 grainers be a decent starting point? 50-52 grains of IMR 4831 with the 160 grainers?

Just load a good stiff load, within upper end of book specs, with whatever bullet and powder combo you choose, jammed .010”. If you can get a “crush fit” thats fine too, just make sure you’re on the shoulder and not the case mouth. You do not want to download while fire forming. You don’t want to jump bullets. I would personally prefer to use the Speer 160’s. Get it fully fire formed and done right first time.


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Drakehammer,

Thanks - I assume upper end of 280 Rem book specs. I meant to keep the bullets generic latter on in my inquiry. If I'm jamming it will almost certainly have to be the Speer 160's.

Yes sir. Upper end of parent .280 case load specs.

This is the method I use for all of the fire forming i have done, bench-rest & hunting cartridges done just the same.


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