Mehul & Ka'imiloa:
Your suggestions regarding obturation of the Snider projectile are quite logical of course, but are not generally found to work in practice.

As you know, the Snider is an evolution of the Enfield muzzle-loader, designed initially to use scavenged Enfield barrels and also the vast stocks of cast projectiles the Brits had stockpiled for the many wars of Empire. In the muzzle-loader, initial combustion at firing obturated the hollow-based minie-type bullet into the rifling just as it started to move, and all was well.

However, when the minie is loaded into a brass cartridge case, and the chamber mouth is bore-diameter only, as in the Snider, then the bullet obturates inside the case-mouth at firing and is therefore not fully expanded to groove diameter when it leaves the case. The problem with the Snider cartridge is that the powder charge is not large, and pressure drops below that required to continue obturation before the bullet completely exits the case-mouth. The bullet therefore enters the barrel while smaller than groove diameter, and stays that way. Accuracy suffers of course.

The Brits developed the clay or wooden base-plug in an attempt to continue expansion of the skirt after the bullet entered the rifling, and the final marks of ammunition were apparently fairly successful. A real headache for the home-reloader now-days, though. This is why I made the suggestion to open up the chambers slightly so that a groove-diameter flat-based bullet could be seated in the case.

In the US, other Snider shooters have solved this problem by developing a 'heeled' bullet, whereby the front of the projectile protruding from the case is groove diameter in the manner of a .22 rimfire bullet, and that is another option.

There was a very good article on reloading the Snider cartridge in a British 'Guns Review' magazine many years ago, if you want to retain the original chamber and shoot minies. Those guys cast their own base-plugs out of plasti-bond if I recall! Otherwise read Coyote's articles on the British Militaria Snider forum here: There's an 8-page 'sticky' over there on Snider accuracy: CoyoteAndMommote's posts start about page 4.

Apologies to Ka'imiloa, I didn't mean to cloud the issue of reloading for Mark's lovely Braddell rifle, however the business of getting the Snider cartridge to shoot well is not as simple as it sounds!

I dabble with a 3-band volunteer-pattern Mk.III by the way, made by Barnett of London.

Have fun!