If I'm about to drop several hundred bucks, buying something from someone I've never met, and never will meet... Someone who tends to ask for things like "money up front", someone who really offers me no insurance that I will get what I pay for, and no recourse should the offer go wrong...
I'm going to ask as many questions as I wish.
If you're selling something for $500, and you have to take five minutes to answer some questions and clarify some issues, and generally prove you're not a thief.. Well, that's $6000 an hour.
If you have to answer 20 such PMs... That's STILL $300 an hour.
If you're the kind of guy that loses his sh!t because someone wants clarification... Well, you don't get my cash.
Put yourself in the buyers shoes... Would you buy a car from some guy across the country, who uses a fake name, and provides one pic of said car?
Besides... Too many people sell stuff in the classifieds like they're selling antique paintings.
I have no way of confirming that you've installed the worlds greatest combination of parts, nor can I confirm that you did the job correctly. You bought it, got it home, opened it... It's USED. It is no longer "new", more power to you if you can charge twice what it's worth, but it wont be from me.
I work hard for my money... I'm going to ask questions. Lots of questions. I will ask questions to satisfy every curiosity I have. I'm not only asking them to find out about the gun, I'm asking to find out about the seller. You want my money? Work for it.