If a transferee/buyer’s ID or DL only shows an initial for their middle name they are still required to record their full legal name in Section B, Q9 if they have one.
The ATF Form 4473 Question #9 heading requires the Transferee/Buyer to record their Full Legal Name. If part of their legal name contains an initial only they must record the initial followed by “IO” in quotes. If they do not have a first, middle, or last name they must record “NMN” in quotes.
In this case the transferee/buyer must provide a valid government-issued document to satisfy the identification document requirements of the law. This supplemental documentation must be recorded by the seller in Q26.b of the form 4473.