That's possible. I have access to some very large boxes at work, which may end up being the route I go. I found some proper sized boxes online, but I'd have to buy a bundle (usually at least 15) because they do not sell them individually. I'll call around to some shops in OKC on Monday to see if I can find anything. I'm looking for something at least 55x8x4 to cover the dimensions of the Remington box. I've got a little bit of time though. I spoke with the buyer today (seemed like a very nice guy). He elected to pay for the shotgun via USPS Money Order. Going that route, it'll take a couple of days for it to arrive, which gives me a little time to source a proper sized box.If you can find a really big box (like an appliance came in), you might be able to measure the size you need, cut the cardboard accordingly and then fold it inside out (so plain cardboard is facing out).
Then put the factory Remington box inside and tape it up really, really good maybe?
Just guessing at a solution.