Verbal contracts are every bit as binding as paper ones
I believe that in some states, verbal contracts do not legally exist: if it ain't signed and on paper, then it just ain't.
Verbal
agreements are ethically binding in all 50 states and beyond--if I give you my word, I'm sticking to it, barring
force majeure--but hard to enforce.
$150 was likely not going to cause him to lose his business; treating a customer like will cause him to lose business. I won't patronize his place again and advise my contacts to avoid him.
Absolutely it is your right to do so. (But, does it seem somewhat petty to bad-mouth him after you bought the gun at a fair price--I assume it was a fair price: if it wasn't , why'd you buy it?).
And absolutely his right to treat customers as he sees fit. True, most gun dealers I've dealt with were more concerned about keeping customers happy (for return business) that making an extra few bucks on any given sales, but who knows? Maybe he's got gobs of customers.
Hypothetical--if you dropped in the next day and the gun was already SOLD (at whichever price), and the guy said, "Yeah, I remember you said you might come back, but this guy had cash and said, 'I'll take it NOW.' So I sold it."--would you still feel gipped? I mean, it not like he said to you, "Well, since you're interested, let me just take it out of the display case and store it in back so no one else buys it before you get back," is it?