Mel and Enfieldlock - to whom many thanks for the VERY informative email.
Yes, it does have a lock in no way different in appearance to the RSAF lock, except that it has a fly, being intended for the use of gentlemen shooters of the Volunteers and their precision shooting at targets, rather than the mass of common infantry oiks, who, in general, shoot at a mass of other infantry oiks.
The original Pritchett bullet came in two diameters - .550 and .575. As the bullets were smooth-sided, unlike the Minié that has cannelures, it was paper-patched to suit the bore, and loaded via a purpose-made cartridge of great complexity. To aid its expansion into the bore, Pritchett and pal Metford -hence the name Metford-Pritchett that you will oftbetimes encounter when reading about this style of bullet] it has a slightly dished bas - nothing like the conical cavity of the Minié, but enough to upset the bullet into the shallow rifling that was the trademark of both Metford, and Pritchett, who designed his own three-groove rifling.
The British Army of the day adopted both the Pritchett bullet AND the Minié bullet, and both were taken to the Crimea, where they cause utter carnage among the musket-shooting Russians, especially at the Battle of Inkerman, where the 54th Highland regiment held off 15000 Russians, causing the slaughter that was noted as looking like the 'passage of the Avenging angel' [of death]. Over 5000 Russians died, and many more again were wounded, perhaps as many as 7000 - the bullet would often pass through two or three at a time, and that has just GOT to sting. It's also the title of Brett Gibbon's excellent book, BTW.
The Minié bullet, which is about 1/5th to do with Captain C-E Minié, had a long pre-adoption history both in France and at the School of Musketry at Hythe with a variety of material being used for plugging the conical cavity in the base. It's hard to believe now, but the actual WEIGHT of the Minié bullet was 535gr, and to make it solid in the base would have made it heavier. That cost more... Anyhow, both the hollow base bullets initially were tried with iron cups - which had a habit of flying out as the bullet left the muzzle - and in any direction. Brett makes HIS cups out of brass, BTW. Being poor, I'll be using Isopon in a correctly fitting Minié bullet - sadly, not a single one of my four Minié moulds throws a large enough bullet - the muzzle bore measures .575"...
So wooden plugs were tried, as were fired-clay and there was little difference between the two. To get more detail you'd have to read Brett Gibbon's other book - 'The English cartridge', which uses well over a hundred pages in explanation.
However, your pal and his sawdust concoction might as well fill the base with Marmite, or the jam of his choice - neither will work any better that his present notion, which is, quite frankly, a waste of good sawdust.
As far history goes, any smooth-sided bullet of the genre tends to be called a Pritchett bullet, particularly by the Americans who used it and the Minié in their imported Enfield rifles - both sides, in fact. The Americans loved them both in equal measure, and were quick to take up the manufacturing of their own 'English cartridges'. In the North, they were made by machines, as were the 'pressed' - not cast - bullets of astounding similarity, one with another. In the south they were made by wimmin, girls and boys, and cast.
The end-results of that culminated at Appomatox Court House.