The timeline is not the point, and has nothing to do with whether it was a straw purchase.
I'm inclined to think of it as a straw purchase myself, in spirit, but you asserted that Black transferred the gun to Rittenhouse on that night, and the timeline undercuts that contention of yours. Now obviously Kyle had been coached on what to say, but this is what he actually testified to in court:
Binger: You had arranged to have Dominick Black purchase that weapon for you in Ladysmith, Wisconsin in early May of 2020. Is that correct?
Rittenhouse: Um, we were up north shooting, not shooting, going camping, and Dominick Black brought his rifle and we were talking. And I was like "Hey, what if we get a rifle for me. Um, I'll give you the money. You can purchase it. It's yours until I'm 18, so I bought the rifle for Dominic, and I can use it, but once I'm 18, um, we can uh do a private sale, and we can have it turned over to my name once I turned 18.
Binger: Because you knew as a 17 year-old, you could not have that gun. Correct?
Rittenhouse: I knew I could not buy that gun.
<Binger gets schooled>
Binger: It wasn't just unlawful for you to purchase it; it was unlawful for you to bring it home. Correct?
Rittenhouse: In Illinois I wasn't able to bring it home because I didn't have a FOID card, a Firearm Owner Identification card in Illinois.
<Some talking about FOID cards in Illinois>
Binger: So you knew that without that FOID card, the gun could not go back to your residence in Illinois, correct?
Rittenhouse: Correct.
Binger: And you agreed that the gun would be kept at Dominick Black's stepfather's house here in Kenosha, correct?
Rittenhouse: Uh, because he had a safe, yes.
Binger: And you agreed you wouldn't have access to that gun, correct?
Rittenhouse: Um, we agreed that the only time I would use the gun is when I was with him and we would go to like the Bristol shooting range or up north to his land.
Binger: But the only time prior to the night of August 25, 2020 that you ever used that gun was up in Ladysmith, correct?
Rittenhouse: Correct.
What kind of f*ked up straw purchase is this where the actual buyer can only use the gun when he is with the transferee? Note that on the night of August 25, Kyle
was there with Black. They did get separated, but they were there together that day until then. I think this arrangement was stupid, especially since if the feds had managed to attempt a prosecution before the gun left the store, then they'd have an infinitely stronger case because Black would only be able to
claim that he wasn't going to just hand it over to Kyle rather than keep it, and then the jury could decide whether they believed him (probably not). But they didn't. And in the interim we see Black acting as if he were the owner of the gun, retaining possession of it, and Kyle never having used it for months after the sale. This corroborates their story, and the question is not one of facts but of how the facts are characterized. Does funding the purchase of a gun that is
kept by the transferee, only to be used in the presence of the transferee, with an agreement to transfer the gun
legally to the funder at some distant future date imply that the transferee A) was not the actual buyer under this fact pattern and B)
knew he was not the actual buyer? As soon as Black's state case is finished, we may see the feds swoop in and charge him, but that's the case they're going to have to make.