As for straw purchasing yes. The very definition of a straw purchase is buying for someone who cannot legally own it or otherwise does not want their name associated with the paperwork. See post #69.Is there a differentiation between buying for someone prohibited and someone not prohibited from possessing in the context of straw purchasing ? Looks to me that the OP, nor the grandson are prohibited from possessing a firearm. I assume that the firearm was already paid for by the OP so the ffl will only have to do the 4473 and transfer the gun to the grandson. Does it matter who paid for it ?
As for does it matter who paid for it? No.