The admission in court was Rittenhouse received his unemployment check, said something to the affect that he’d use the money to buy an AR15. He then gave the money to Black to buy him the rifle, which Black would secure at his dad’s place, until Rittenhouse became legally allowed to own it.
The government need only prove the intent of the “gifting” was to allow the purchase of the firearm for a person not legally allowed to do so themselves.
I don’t know where you are getting your information from, but maybe you should sit down with 18 USC Section 44, and 27 CFR for a bit?