Gains on gun sales are not that much of a risk these days. Just like antiques, gun values are lucky if they are holding steady. I recently settled an estate that was filled with antiques. The value of which was down about 40% from an appraisal from less than 12 years ago. Same person, did both but values were way down and they did not think that they would ever recover in some cases. Furniture, China, silverware, glassware were all down. Some Oriental rugs were up slightly but several were down. The appraiser saved thousands of dollars in estate taxes because the value was just not there anymore.

Its the same thing for guns. A few may be way up but most are level or down from historical values. And we are running out of old men entering the gun collecting market. Less competition means less demand and less pressure for increasing values.

Technically you are susposed to report gains on sale of personal property. But you must be able to prove what you paid for them. Few keep records. Unless you are selling vast amounts of guns I doubt even the current IRS will get too picky. They might if they catch you playing other games and see deposits for items sold. But thats a reason not to be stupid in the first place.