If it was a credit card purchase, just contest it with your credit card company. What if you didn't want a Buttpad, but just a flat plastic or steel buttplate?
I've found that when people learn the credit card company is going to tell them the customer won't get their money back, they decide just to refund all your money. You might still be out your $8 return shipping though, but it beats the $27, and it shows a merchant they can't treat customers like that.
Especially if you have emails where he admitted there was a chip. Just contact your CC company, they'll send you a form, print all the emails, attach as proof, and see where it goes from there. Might call the CC company, see if they are going to be on your side, then tell them to send the form. Call Gunstocks back, tell them you talked to the CC company, they are sending you a dispute form, and you are filling it out and mailing it. Don't threaten them, but sometimes they might chirp up and give you back all your money. If they say fine, go ahead, then just follow thru. His precious time will get eaten up dealing with the situation, or else he will lose his money if he doesn't respond to their inquiry.
I have nothing agaisnt the company either, as I have received a satisfactory product before. But if the company doesn't do the right thing, I usually stand up and do my best to make sure they do, otherwise, they just learned that crapping on the customer keeps them money rolling in.