Originally Posted by
Ballistics in Scotland
Pipe caps are usually either screw compression brass or solder-on copper. The latter would thicken up as they are drawn lengthwise.
One possibility is Magtech brass 32 gauge shotgun cases, which although centrefire, have a hollow rim into which a wet primer paste could be spun by centrifugal force. They have a head about .03in. larger in diameter than the Vetterli case, but I don't think that is too much of a forming job. You could seal the primer pocket with a used primer from anything.
The 7.5x53.5mm. GP90 round for the 1889 Schmidt-Rubin rifle is an interesting one. The bullet has a heel under the paper patch which is totally unnecessary for the usual purposes. The main surface of the bullet is considerably less than neck diameter, it isn't outside lubed, and the chamber is much wider in the neck than the otherwise almost identical 7.5x55. Datig, in volume 3 of his “Cartridges for Collectors” illustrates not only the GP90, but another, misplaced among the 8mm. ones, described as “7.5x53m/m Schmidt-Rubin Model 1889”ar. I believe this one had a heelless bullet, with a bullet which carried the full GP90 bullet diameter, about .321in. including patch, all the way to its rear end.
So why introduce a heel? Possibly so that any finning of the soft bullet would take place at that step, a much less harmful place than the edge of the base. This is what we may be seeing in the Vetterli bullet illustrated here.