You'd have to set up some heavy duty exhaust fans on the unit to get rid of moisture and lead dust. I'm not sure how you would set up the bullet trap.
Not necessarily..
If you are shooting from outside of the box, and using it as a trap..
Lead dust isn't dangerous unless you are standing in an unventilated range where they are putting a couple thousand rounds down range in a short period of time..
The range I shot at as a kid (at least twice a week for a few years) wasn't well ventilated but we were only in the "range" while we were actually shooting, and only shot about 100 rounds per day, in 10 - 20 shot increments.
A police officer died in his sleep (drowned) from what they assumed at the time was due to lead exposure, BUT he spent the entire day inside the shooting range while hundreds of fellow officers qualified/ practiced. Thousands of rounds in less than an 8 hour period of non-stop exposure.
I wouldn't think a shipping container wouldn't need fans, or scrubbers as required for indoor ranges today, but would put in cross ventilation (holes), and NOT shoot inside the container with the doors closed (or open for that matter).
I've also shot in "indoor" tank ranges.. where the tank was under cover, and the targets were under cover, but between the two were a lot of open uncovered ground.. If you shot at say 1500 meters, you shot through the covered 250M, 500M and 1000M covered shooting spots, and into the covered/ enclosed target area. All the benefits of indoor range shooting, with no concerns about airquality.
We lost THOUSANDS of indoor ranges in the US due to the EPA and OSHA rules for venting and scrubbers, and in probably >90% of the cases the requirements were total overkill.. not enough rounds downrange in a given period to be a concern. (for example, almost EVERY national guard and Reserve unit had an indoor range.. SMALL, two position MAYBE three.. no way to get enough rounds downrange to cause harm, but the requirements were too expensive to implement.. and actually closing the ranges, and recovering the area for workspace was to costly. HAZMAT remediation removing the sand and lead from the traps was too $$ so several of the centers still have the ranges, they're all just padlocked and abandoned.
