I have the same rifle, silwer barrel and plastic stock.
I have shot 2 warthog and a springbuck with mine, 0.490 roundball patched. We are using Sannadex powder in South Africa(pinkish coloured) and I'm using 85gr(volume) pushing the R/B at 1700fps.
A realy nice rifle, I replaced my Lyman Trade with it since I was scared of scrathing/bumping the wooden stock.
My rifle are on my shoulder when I'm on the farm and that is almost every weekend, sunrise to sunset