If you are going to the trouble/expense of upgrading the barrel and hop unit, then yes, it would seem to make sense to put in a quality bucking. I personally use Maple Leaf (look up the pro's and cons of decepticon vs autobot and silicone vs rubber), and ensure that you choose the correct hardness (expressed as 'degree') - 50 degree would probably be optimal for a pistol. I hear that Flamingo buckings are also highly rated, but I've never used them myself.