phorton. COAL for the 280 is 3.330" and if your using Barnes data the start load is 52gr/H-4841SC max 55gr/H-4831SC and Barnes has the COAL @ 3.270" with load density at 92% for their 140gr bullet.
If your using IMR-4831 51grs to start max 54.5gr load density 95% in the Barnes manual for 140gr bullets.
I don't have any IMR-4831 or I dump some in a 280 case but I dumped 57gr/H-4831SC and I had over 1/2" before bullet touch powder and 150gr TSX if I seated those I'd hardly be compress @ 3.330".
If you got short throat and these longer bullets take up case capacity best to switch over to a FB bullets they be little shorter than BT. Before you think about having longer throat might want to check magazine length.
My 280AI was factory Rem in 280.
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