270 Improved Short Magnum Dimensions

From This old Die, Stamped "270 A A F IMP S MAG", Using 7mm RM brass. 2.53"in length & the shoulder is a narrow .46" and the Neck Internal Dimensions measure .248" after running through the Press without an expander button in place. The Die left a ring on the Neck just over .03" down. (This is Not my Ackley Die Set, sorry, my mistake. The Die bottoms out on top of the Belt.) I don't believe this is based on a Belted Magnum. The base ID is close to .511". 2.28" OAL if using 9.3×64mm Brenneke-based brass or something similar. Thus making it a very short Magnum indeed.

Not sure what you are asking, or stating, at all.

But for a .277" diameter projectile, a .248" inside neck diameter leads to something being way off. You should not be reducing that much, then having to expand back to approximately .274-.275" neck ID, either with a button or expanding mandrel.

This is all I found:

~ From the base to start of the shoulder is 1.9075", with a diameter at that point of 0.490".
~ Base to top of shoulder is 2.0786".
~ Case length 2.450".
~ Shoulder angle is 28*.