I am not sure ANY pistol (even the much vaunted .500) is ideal for large brown bears. I prefer more, like the .375 H&H or above. If the Glock 20 it is, though, I would load it with heavy loads from Norma, or Buffalo Bore has a hard cast and a FMJ that I would go to. The Glock is probably a good choice for AK (the weather resistance) and I have found it as comfortable and reliable as anything else to shoot with the 10mm, which ,besides the .45 ACP, is the only auto round I care for. The 10mm/.45/.44 arena are good to buy some time to get to the house/truck and get a nice .416 Rigby into action. The problem is the shooter. Yes there are those individuals who can make a perfect shot all the time, no matter what. Then there are the people who can make the perfect shot and drop them when everything goes right. With bears things rarely go right (they are like us in that respect) and you can't plan for what may do the job under certain circumstances, you have to plan for what will clean up the mess when everything goes to total ****. You are never prepared for any situation that any animal will throw at you unless you lug a .577NE around all the time.