The ogive shape of the bullet determines how long a cartridge can be loaded relative to the throat depth, that's the problem with the 405gr Rem and 400gr Speer and even most 350gr, their fat ogive makes a big difference compared to the smaller 300gr bullets. You can see the difference in the comparison below, L to R, 300gr Speer, 300gr Rem, 405gr Rem, 400gr Speer FN, 350gr Speer FN, 350gr Hornady RN and 350gr Hornady FP Interlock.
I can load the 400gr Speer to 2.764" where it just touches the lands, that's right at the bottom of the lower cannelure. Haven't shot it yet, I've done some testing with the 350gr Hornady RN and 350gr Speer FN, 100yd accuracy in the 45-70 BC with the 350gr Hornady was outstanding at 2027fps.
Tim
