I've used DuraCoat for several projects. The DuraCoat is a pretty durable finish IF it is prepared properly... I did a pistol and coated the extractor. About a year and a half later I decided to polish the finish on the extractor... I used several grades of emery cloth and paper... and I must say that I was impressed. I got some off the edges, but the bulk of the finish has taken hold of the metal and it just won't be sanded off without some very firm determination.
A few things to watch for...
Get a good finish on the gun with best metal finish and be very sure you have it completely degreased.
Realize that the finish is an epoxy mixture and if you use the full mix of hardener... to get the best finish... you can have the mixture set up in your sprayer and it will just about ruin a spray gun if it sets very long at all. Also realize that if you have the color for some time it can thicken and again make it impossible to get through the sprayer.
Aside from these issues, it will provide a very durable coating... read carefully and prepare thoroughly. Don't try to put too thick a coating on at one spray, etc. When you get a good finish you will be happy with it for quite a while.