Agree, forearm needs some shaping and the barrel sight looks very out of place - both literally and figuratively. And for a good, accurate Brit .45 round? Why, 500/450 no.2 Musket of course, my personal favourite! Going with a BN cartridge usually eliminates - after fireforming - any rim thickness issues, as you can headspace on the shoulder.
I use some converted Kynamco 500/465 brass in mine, which has much thinner rims - works just fine...