Finnish firearms expert P. T. Kekkonen ran a web site, “Gunwriter’s Questions and Answers” where he addressed various gun-related issues. Unfortunately Kekkonen passed away, but his site remains. If you scroll down a bit, he goes into a lengthy and quite interesting account of bullet design from round ball to the modern full metal jacket. Included is this description of the Pritchett bullet, which I have mentioned before as being favored by the sharpshooters.
British-designed Pritchett bullet was smooth-sided, with a shallow base cavity. It was possible to produce these bullets by swaging from lead cylinders and so avoid faults of cast bullets. Pritchett bullets were popular in the American Civil War. Caliber was .577 while American rifle-muskets were usually bored to caliber .58 (14.7 mm). Bullets were wrapped into lubricated paper patch. Some clearance between bore and bullet was therefore needed for muzzle-loading. Not only the hollow base but also the cylindrical solid shank expanded to become groove-filling by the blow of powder charge and gasses.
As Kekkonen says, swaging — that is, forcing a lead slug through a sized opening — gives a much more precise and repeatable bullet than casting. Unlike casting, swaging requires a well-equipped factory, but makes for a much more consistent product and thus better accuracy.
Well worth reading to get a sense of how bullets developed in the 19th and 20th centuries and how design affects “tappokriteeri” — Finnish for “killing criterion.”
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