When faced with screw in bowls for Falcon or Viking pipes, be aware that they are NOT interchangeable. The Falcon has a four start thread, enabling a quarter turn to lock the bowl onto the pipe. One added anomaly is the Alco (also made by Falcon), whilst looking the same is actually a different size. There are very very few pipes with this Falcon style thread.
The Dr Grabow Viking bowls have a single thread and there are very many bowls which will fit. You should never force the bowl onto any pipe, if it does not go on quite easily, it probably means you have the wrong thread. If you value your smoking, be careful of any stamped Mexico, these tend to be as much putty as briar !
The metal pipes with a bowl that attaches to the stem by means of a metal screw through the base of the bowl can be difficult as the head of the screw is often badly worn. I suggest you foregt the screwdriver orute and instead get an Easi-Out 5/64 inch ( 3.5 m/m). Using an Easi-Out into the smoke hole should free the screw without making the head any worse and without seriously affecting the smoke hole. For the un-initiated, with an Easi-Out, turning the tool anti clock wise drives it harder into the hole, while undoing the screw and should free all but the very badly corroded screws