A conviction for using a firearm in the course of a robbery precludes increasing the underlying sentence for the robbery itself for explosive or weapons threats, even when those threats are unconnected to the firearm used in the robbery.
http://media.ca7.uscourts.gov/cgi-bin/rssExec.pl?Submit=Display&Path=Y2018/D08-31/C:17-3236:J:Scudder:aut:T:fnOp:N:2211361:S:0
Since 2011. An occasional commonplacing of the U.S. Circuit Courts of Appeal.
Neither an authoritative statement of the law nor legal advice. Quick work.