The dealer is blowing smoke you know where. All firing 300 or whatever the number is, is polishing the internals, and seating all of the parts. On a pistol over $1000.00, that should already be done by the manufacturer before releasing the firearm.
If the gun doesn't fire, you have evrery right to ask for either a refund or a new gun. I don't know what state you live in, but most states like mine give you 3 days to return anything for any reason. I know this because I owned health club.
They don't even have to give you a reason, it's the law. you never listen to salesmen on issues like this. You go right to the state.
Also if you post a complaint on the better business bureau's website in the locale, he is in. You will be surprised how quicklly his attitude will change. I have used it myself twice, with a tv and on a plumber who re -did my kitchen, and refused to come back to instal an allen screw that held on the faucet. Basically he told me to f off, after 8 grand in plumbing work.
Don't allow people to bully you, if I wanted to spend another few hundred dollars before being able to fire this gun, I would not have Purchased it, that's your stance. I hate bullies, when I got through with brandsmart, I became best friends with the VP. She fired a whole bunch of people and told me they spent 4 thousand dollars repairing a 1,500 dollar tv. People can be very stubborn and stupid. I ended up with a Gift certificate for a new TV after it broke a second time with 8 trips and 6 months without my TV.
Don't let people push you around, explain your intentions and offer him the oppertunity to make amends. Let him know that once it starts, it's on. And you will put your experience with him all over the internet, facebook etc, you have weapons you aren't using in this fight.
As a few guys mentioned the firing process can be set aside by using the proper polishing compound on the rails and the feed ramp, also the firing mechanism where the top round hits the slide from the mag. I would be happy to help you any time if you PM me, after hundreds of pistols, I can pretty much tell you where to look and how far yo go. That is all that firing thr rounds is doing, just removing high spots burs etc.