Did Fancy Prancer Rants mention that Masen was about the only source for 6.5mm Carcano ammo in the Dallas area back in 1963?
No, Lance more accurately mentioned that the FBI determined after contacting the manufacturer and canvassing numerous outlets that Brinegar was the primary source in the Dallas area, that Masen had obtained his M-C ammunition from him and that the two of them were the only Dallas-area sources. There is no reason to suppose that Oswald obtained whatever ammunition he had from either Brinegar or Mason, the only evidence one way or the other being their statements that they didn't recognize him. Ammunition could be bought by mail in 1963, and I would imagine Texas and Louisiana were as lenient as any states in the union.
As others have sagely pointed out, you are a troll and a bore, and your efforts to make others look silly consistently backfire and make you look like a buffoon. You have enough knowledge to make useful contributions, but you desperately need a new act.