I finally managed to get my hands on some Speer 400 gr JFPs but, after reading the FAQ about the Handi's short throat, I set about measuring how long a cartridge it would take with this bullet.
Answer = 2.50"
My Hornady 300 gr JHPs and 350 JRNs chamber just fine at the standard 2.55".
The good news is that I have some Hornady LeverEvolution brass which is on the short side so I can seat the 400 gr bullet to the front cannelure and stay at or under 2.50". But I'm thinking I need to moderate the charges for the short COL.
How much difference does a 20th of inch make in terms of pressure? Anybody have experience with this?