I've not looked at any of the gun auctions you list - much because I am one of those "put it in my hands" people who want to feel and caress the gun and see how it feels prior to actually making a purchase. Even guns that are the exact same may not feel the same when you hold them(personal opinion).
That being said - I'm very active in the PennyAuction world - I'm a software developer and that is what I do for a living. So since this topic of auctions has come up I figured i'd point you guys at it.
www.guns4pennies.com - now mind you that this is not your typical bidding site where you just go on and bid what you are willing to pay. That's not how Penny Auctions work. But i'm sure if you look at the site and find something you want you can probably get a great deal (that's how PennyAuctions work).
I am not affiliated with this particular site in any way, they do not run my software, and I'm not even a member of the site. I actually found it on another forum that is for that industry that I am a member of.
A little detail on how Penny Auctions work for those that don't know - You sign up and pay for your bids. Each bid costs you something like .50 cents (each site is different) and you can then place bids on items they have for sale. Each time you hit the bid button it deducts a bid from your account and adds a little bit of time to the timer. This continues until no-one bids and the auction runs out of time. The person placing the last bid being the winner. On my own site I've seen people with things with 1 bid and get an excellent deal, I've also seen items go way beyond the retail value when a user wanted to make a "don't mess with me" name for themselves. When the auction is over the final bidder then pays the final auction price and any shipping fee that is charged.
I'm not endorsing the PennyAuction industry - just showing another Site that has a little different spin on auctions that is related to this industry.