That may be exactly what you are smelling.
I'll probably be keeping them sub-sonic.
Shot some MBC 210 gr. coated 44's today from 650 to 850 fps and did not notice any unusual smell.
My indoor range has almost hurricane like ventilation that blows one from behind and down the range.
Since it was single digits F. today I had to keep my coats on.
Yeah plural coats. The vent air is fresh from outside.

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NEMO
"Everything 44"