The instructions on the 3310.4, Q7.b, says:
“Copy 2–To Chief Local Law Enforcement Official (CLEO). The CLEO is a local or State official designated to receive this form. If you do not know your CLEO, contact your local ATF Office to find out. Provide Copy 2 to your CLEO”
The ATF further clarifies where the multiple sale report should be sent on this page. On this page the ATF says “A copy is to be sent to the designated State police or the local law enforcement agency in the jurisdiction where the sale took place.”
If you are at a Gun Show or Qualifying event that takes place in another town or city within your state the multiple sale report must be sent to the CLEO in the jurisdiction where the sale/transfer of the firearms took place. This could be the same CLEO or it may be a different CLEO. If you are unsure you should follow the instructions on the form and contact your local ATF Office to ask.