They're not easy to find. A friend of mine, a shooter, has been
looking to get a suitable instrument case for ages.
His latest production was "the Black Russian", an enormous
leather-trimmed papier-mache codpiece / riflecase, to suit an equally
enormous .577 Snider. Laid up with brown Kraft paper over a polystrene
foam former it took a huge amount of effort to produce a device of
surpassing ugliness. It didn't smell much better either, owing to the
quantities of xylene used to dissolve out the foam.
Commercial instrument cases (violins and cellos anyway) these days are
rotationally moulded polypropylene. It has _much_ better impact
resistance than all the alternatives, including aluminium or GRP.
Looks cheap, but it preserves your instrument.
Look for briefcase hardware. I've replaced several briefcase latches
and I think they are identical to the ones on my son's trumpet case.
(too far away right now to go look)
As for building the case, you might also look at briefcase plans (I
think Rockler has them) the basic idea is similar and it should get
you going in the right direction at least.
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