When I read threads like this I often think of this statement. All Poodles are dogs. Not all Dogs are Poodles. The word "Custom" as it pertains to guns and other things means different things to different people. To some people it means any changes to the gun vs its factory stock configuration. For others is mean a complete overall of the gun to include mechanical parts all the way up to grips and cosmetic changes. To me the word custom is often used to describe everything in between. People need to understand the wide variety that falls under this large tent definition.
In one sense all of my Glocks are custom because the first thing I do is swap the OEM factory sights. On the other end of the spectrum I have custom 1911s and BHPs which only the frame slide and sometimes the barrel are retained. Everything else is swapped out. If I took one of my Glocks out of the safe and sold it I would not lose any money. The mods which make it custom are easily undone and it is almost universally understood that Glock OEM sights suck balls and need to be replaced. The replacements on the gun add value they do not diminish the value.
The same can be said for my customs BHPs from Ted Yost, Don Williams, Jim Garthwaite, Jim West, APW Cogan etc... The mods might not appeal to everyone. It may narrow the pool of potential buyers but because I had a professional gunsmith who is nationally known do the work and have the providence to prove it these modifications and any potential buyer can see what was done and it was done by a craftsman not Bubba under the shade tree. I am not saying that the OPs gun falls into that category but many "customs" do.
The other big part to me about resale value is are you customizing something that a lot of other people customize in the way you are modifying the gun. Like my Glock example. BHPs are similar. It is pretty universally understood byh hardcore BHP shooters that FN/Browning OEM sights are not the best of the breed. A buyer who wants a functional working BHP will welcome a properly dovetailed set of sights and will pay for it in my experience. Where "value" gets hurt are mods on guns which are not often modified or when the modifications become too personal and narrow the appeal of the finished product.
Extreme levels of customization can hurt value but if they add to the owners enjoyment I am not sure you are "losing" money on the modifications. Guns are poor investments. The "value" I get from them is owning them and shooting them. If I was investing for profit and resale there are better options IMHO. If I "make" money on enhancing my collection that is a bonus not the objective.
In the end I always make a pistol mine if I intend to keep it. That means grips, sights, finish changes etc.... If it is more than simple changes I have them done by known smiths and keep the records. In the end I don't worry too much about resale value. I horse trade guns all the time but the core ones pretty much stay. Their long term value is something that my heirs will have to deal with but I have given them enough providence that they will be ok. The other part which needs to be accounted for is that proper custom modifications allow an individual shooter to shooter a particular gun better than the stock guns. The value of this modification is huge to the individual who did it but might not translate to the next owner. Modifying a sporting clay shotgun to "fit" the owner comes to mind as an example.
Here is another perfect example. It is Ted Yost Browning Hi Power. I was a simple MKIII with a forged frame. I sent it to him and we went over the build I wanted. We went back and forth on some of the details and in the end this is what I chose. It is a better shooter than when I sent it to him. When we talked about what a BHP "needs" Ted said, and I am paraphrasing a bit "It really needs only 3 things to take it from an very good gun to a great gun. A great trigger, great sights and a great safety. Everything else we do to them is to make them beautiful because we want to." It has been shot. It has been carried a bit. It goes into a holster and it has had mag changes done with it at speed. Even with those considerations I would not lose money on this gun if I sold it today.
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