My main reason is to blend in, break the outline, sometimes in the case of a Fiberglass stock, it must be covered with something, and also in some cases, texture, you can apply a little truck bed lining around the gripping areas, then paint over that. Most of my painting has been stock only, but my scout rifle and Marlin 336 got the whole treatment, scout rifle barrel, scope, butt cuff and ammo ( just kidding ). Of course if your blind hunting the camo makes no difference, if your stalking or in the combat zone, I think it helps, even if it gets a little chewed looking, it will blend in better.
I have not done it, but I suppose a lot of you have seen snipers using burlap strips, sometimes dyed sometimes not, like a ghillie suit, wrapped around the rifles forend, it makes for amazing low cost camo. My thought was to use fiberglass resin and make this look permanent instead of field expedient.
I think this is from enemy at the gates.

4th 5th and 6th from the left.

Because that is the way the Marine corp did them, the metal is finished in an epoxy coating, and matte. The paint is much to bright for me, to glossy.


Not the best pic, but my Marlin 336 is done in a subtle black and gray tiger stripe dura coat, with a trijicon reflex, I think it will make an excellent stalker. Picture shows a 3x9, but it has been removed.

It's ok to lust after my 40's vintage Marlin 39a, with Redfield 4x mini scope, wood refinishing by me, to look original oil satin finish.