Another thing to consider . . . order the rifle, and you get a new rifle. The guy is selling a USED rifle. Unless it's some sort of collector's item, I've yet to see a used gun selling at a new gun price, so "equalizing" the price of the guy's used rifle with a new rifle isn't really in line with market realities, IMHO.
I'd say, let him know what a new one is going for, offer less, and see what happens. If he hasn't gotten any other "nibbles" you may get a good deal.
If he's unwilling to sell at your price, YOU have to be willing to just walk away.