Go shoot it, and inspect the bore afterwards. If you have heavy copper fouling in less than 20 rounds, then don’t complain: the rifle was a gift. Some rifles copper foul badly, I had one that in less than 20 rounds I would see dark patches in the bore and the point of impact changed. Not much you can do with a barrel that has a propensity to foul, bore lapping will help, but the bore is larger.
Never rapid fire a magnum cartridge. It will be best to shoot one or two rounds and let the barrel cool down. If you shoot it fast enough that the barrel gets hot, be thankful the rifle was free, because the barrel will not be long for this world. Cartridges that push a lot of powder down the barrel at high pressure eat barrel throats. It has been a month, and now I have forgotten the caliber, but a highpower shooter told me that he had around 800 rounds on one of the magnums, and it went from MOA to eight inch groups at 100 yards.