[mrerick]

To see actual sales prices there, you must have a login.

After signing in, use the Advanced Search function.

Look for a tab at the top of the search area and you'll see "completed items". Select that tab.

Search for what you're looking for, and then look for sales that actually took place at auction with multiple offers. That should give you a good idea of the actual open market for an individual firearm. Be aware that condition affects values on collectible firearms quite a bit.

Be sensitive to the possibility of shill bidders (artificially bidding up prices) and bidding wars between two collectors that want the same item. You can see this by looking at bidding history.

Next, try and find similar firearms in similar condition and then average the sales prices. I tend to not pay attention to "buy it now" listings or the listings that don't attract any bidders, or the ones that attract only a very small number of bidders.

Use a window of about six months and you'll have a good idea of the range of valuation. Try and find items similar to one you own, or one you want to acquire.