A few years back I did some sketch designs for a 100 metre underground range using concrete pipes around 1 metre dia. The land had a gentle slope so the shooting point could be a little below ground level and the target end fully underground. The design included a super size muffler for muzzle blast and the pipe was covered with a minimum of 500mm of earth. The ground was pumice and pretty well drained to get over another problem but the cost was uncertain and likely prohibitive and the project was canned.
During my working days I came across a number of Halls, mostly Rural and one NZDA that incorporated .22 rifle ranges, some shot under the floor and one through the hall and under the stage. All are now closed and some have been for many years.
Regards Grandpamac.
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