Correct me if I'm wrong, but the heat from combustion inside the gun would melt the gold, too, right?
After repeated shots, yes. Gold-plating wepons is a very good way to show off that you're a money-grubbering douchenozzle. Since it serves no actual purpose, you probably should've just gone and bought a few crates of mosins.
Also, it's commonly thought that bolt-action rifles are slow and useless, they are not, people are slow and useless. One lad managed to get 46 rounds out of his Lee-Enfield in a minute, considering the magazine only holds ten rounds, it's quite impressive. It involves having your middle finger falling on the trigger immediately after closing the bolt, and keeping the thumb and first finger on the bolt handle. Takes practice and only really works for surpression fire, but it's p. cool.