The service load for the British and therefore the US Union Pattern 53 rifled musket - AKA the Enfiled - was 2.5drams of fine rifle powder. This equates to 68gr of FFg.
Here in yUK we shoot this load under a 535gr deep-skirted Minié out to 800 yards in competition run by the MLAGB. AAMII, the habit of using base plugs died away very quickly, mainly because in the rough and tumble of the cartridge box, they tended to detach too easily, and the average soldier really had other things on his mind than picking the plug up and putting it back in.
I have a 58cal Musketoon - the carbine of the day - made by Parker-Hale, and cast my own 495gr Minié bullets and shoot them over 55gr of FFg with a high degree of accuracy - groups of ten hover around four inches at 100m if I'm careful. You can see me shooting mine on youtube - go for tacs trains shooting the musketoon -
http://www.youtube.com/watch?v=dvCsmZPBUPY.
Down in the lower 48 a comparatively large number of BP hunters use the Musketoon - it's a really handy brush-busting piece and has a lot of authority at reasonable ranges - 80-100 yards is maximum though due to the self-imposed limitations of good sportsmanship. However, even at that range, with ~65gr loads, you will see the effectiveness of that big end-of thumb sized lump of lead.
Minié bullets work best in slow twist barrels -around 1:48 or so, and are thumb-loaded directly over the charge.
I do not recommend a Minié bullet in an in-line. The charges used in these modern-style contraptions will blow the skirts right out, prolly leaving it in the bore.
tac
P-H Musketoon #1361