getting a 1865 Burnside carbine

[bear tooth billy]

I have an original Burnside Spencer coming. I want to shoot it, so I have a couple
questions. I have a 66 Allen conversion, that I got an accurate mold for, 450 grains
.519". Is this bullet to heavy for this gun. I saw in a previous post about a 320 grain
mold from accurate. First step will be to slug it, as with my limited experience, the
groove diameter can vary a lot from gun to gun. I have 45-1 and pure lead, which
would be the best?   

                    Thanks  BTB

[mgmradio]

I use the Buffalo arms 56-50 bullet mould. It drops at .520 in pure lead and is very accurate and cycles through the action well.