Hi David,
Joining a collectors organization such as the NAPCA (and/or others) opens you up to other buying opportunities as well.
I have added 4 Swiss guns to my collection (and even 1-2 non-Swiss pieces) that never got on the "radar screen".
Some of the NAPCA members sell quitely amongst themselves and at their gun conventions. The SE NAPCA gun convention in August in Chattanooga, TN has been a rewarding trip for me several times. This event is for Members-only or their sponsored guests. Walk-ins are not allowed unless sponsored, at the door or prior to the show, by a member.
Many of the NAPCA member are part of an older crowd of collectors...some starting their collecting in the 1950 and 60's. Lot of these fellows you meet in person in TN do not have computers and are not on the Internet...yet they trade guns all the time to other Members and friends of friends.
Here is an info. link to the NAPCA. Once you are a Member, you get access to their Members-only Internet forum as well.
http://www.napca.net/index.aspx
About the regular gun shows : If you look closely and pay attention, you will see many guns trade ownership "behind the tables". That is, table holders will hold a gun or two under their tables and will not even place it on their tables. When one of their collecting friends show up, a deal is made. It takes some time to get to know these table holders and be part of the "select" crowd that gets offered these "under table" pieces.
BTW...there has been criticism of the NACPA organization of late over the past 2-3 years with many fellows concluding it is no longer current and behind the times and some dropping their Membership or not considering joining. The new Forum the NAPCA has put up has been an attempt to bring this Organization onto the Internet. There are 200 Members on the Forum, now, and it only started this year.
I see my Membership as worthwhile and renew yearly. The $ 50 each year is worth the opportunity for me to connect to some collectors I may not do so with, otherwise. These guys are a treasure-trove of info. to a newer collector, can save you $ Thousands by teaching you what to beware of and some will tell you the "horror" stories of Waffenfabrik-USA going back over nearly 3 decades.