Finding this info of Daryl's quite interesting in that I am putting together a load for the 450-400 3" at present. I have a Saeco 400gr .410 mould on the way to start with and was planning on starting with Trailboss loads in it to get a feel for what I could do with this gun. Once I have the sizing and lube sorted out I want to use a 300 and a 350 LBT LFN with GC to see what they can be taken to in this unit. The one area of concern I have with using cast is powder capacity of the case vs what powder volumes I can work with in this case. I really am on the fence about fillers, don't see anything out there that is really bad, but, enough cautionary stuff to make me waffle a bit on using any, as I suspect they will be req'd for the gascheck loads. I am under the impression that I will need 80% volume filled to be safe without fillers, which I believe can be obtained with slow powders like the 4831's or slower. Just not sure what the results on a cast bullet will be. The part that makes me leery is having to reduce the loads to use the cast bullets. If I can keep the velocities down to the 1800-2100 or a hair less mark with an 80%+ type load, life will be simple, I think.
Main concern is if I need to go to faster powders to make it work. There is some data on www.grurifrasca.net on the faster powders, all with 400gr slugs, jacketed style. Not sure how some of those may translate to the lighter bullet vs speed and the need for fillers would be there also.