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Pressing Business On the manufacture of extruded hexagonal Whitworth bullets by George Arnold |
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I was
sitting in my cabin on the slow boat back to Jersey, considering methods
of making hexagonal Whitworth bullets. Casting is the usual and most obvious
method; but changes to bullet design usually call for a new mould. Not
too many volunteers for that! A swage comprising punch, nose and body
dies is more flexible; but each bullet will require finishing. Whitworth's
method of extruding rifled lead wire, cutting to length, then turning
nose and tail, allows any changes to shape or weight; but is slow and
involves considerable tooling investment. No easy solution presented itself
so brain had been disengaged and I was just sitting, empty mind (and full
glass). Then an idea struck me so hard I nearly spilt my drink! I would
take a plain cylindrical bullet, with a larger diameter than .440"
and push it, nose first, through a hexagon rifled die. If there was enough
resistance, the punch would form the base cavity; and I had a length of
.440" AF Whitworth barrel. Now all those who have tried, know that
if you push a long lead bullet into a substantially smaller die with a
short lead, it will expand too much or collapse. The cunning plan which
had just presented itself was to provide a die to contain the expansion
of the blank until it had passed into the rifled die. There were some
questions to answer:
(a) What diameter
(ø) blank? (a) I had an old pot mould .462" ø which sounded like a good starting point. (b) The rifled die was .470" across corners so .472" ø seemed a good guess. (d) All the toggle presses (the system usual in reloading and some swaging presses) failed as pressure has to be extended over about 2" stroke. Fly, screw, arbour or hydraulic presses all work so long as there is >4½" daylight. The blank is cast
with the required nose shape in a plain mould at least .462" ø
around 1.4" long with a flat base. The weight and nose shape will
not be altered by the presses. Shorter and harder bullets will need
larger diameters; but lapping or boring this type of mould is simple
work. |
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© 2006 G Arnold. First published in Black Powder Summer 2006, journal of the MLAGB |
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