fire forming 280ai or 6.5-280ai brass from 270?

[loaders_loft]

lightbulb
If one wanted to use premium quality norma .270win brass to make ..280 AI brass, how would one fireform it? Neck up and fireform? Jammed bullets or COW method?

How about making 6.5-280ai brass from norma .270win? Same thing, just neck down & trim instead of up before fire forming?

Has anyone actually tried this, or something similar, blowing a shoulder out and forward about .051"

I just wonder...

 

[Jamie6.5]

Regardless of the fireforming method you choose, .280 from .270 requires you to make a false shoulder first by necking up to .30 cal (.308) with an 0-6 die. Then resize down the neck the proper distance with your .280 die, leaving a "donut" at the height specified for the neck/shoulder juncture of the .280AI case.
This will cause the case to headspace on the donut when fire forming.
If these are older/many fired .270 cases I would anneal them first.

Since 6.5 is smaller than .270 you should be able to resize partway down the neck with a 6.5 die, leaving the same "donut" above the .270 shoulder.

Good luck!

 

[loaders_loft]

lightbulbfalse shoulder, gotcha. Thanks for the tip. I recall reading about that before, but it just didn't pop into my head.