I am assuming that your specifically talking about the firearms auctions, that Redding has?
On the firearm auctions, I have been to several and have purchased rifles and shotguns. It is nice that Redding publishes a list of the firearms to be sold on the website. So you can come up with your wishlist. The biggest problem I have ever encountered, is if a real collection is being sold, for example a estate is selling a Browning, Winchester, or Garand collection, more "collectors" come out and the prices go crazy. They had a Garand collection being sold a couple of months back and I saw "Service Grade" SA and HR Garands selling for over $1K, when they go for $600 on CMP.
If you are looking for a rifle or shotgun for actual use and do not mind buying a used firearm, then you can go and find a good deal. The last time I was there, I was with my Father-in-Law and he bought a like new Benelli Super Black Eagle II 12 ga. for $750, and they retail for $1500 or so.
If you are looking for a collectors piece, then go and enjoy watching otherr people pay some really high prices.
Expect to pay more than the gun is worth if you're buying it at the auction, I've only seen one or two good deals on guns there. Accessories are what tend to go cheap.