The effectiveness of a 44 Magnum handgun against a grizzly bear depends on a number of factors, including the size and aggression of the bear, the distance from which the gun is fired, the quality of the ammunition used, and the skill of the shooter.

Grizzly bears are one of the largest and most dangerous land animals in North America, and they are known for their formidable size, strength, and aggressiveness. When confronted by a grizzly bear, it is important to have a firearm that is capable of stopping the bear quickly and effectively.
The 44 Magnum is a powerful handgun cartridge that was designed for hunting and self-defense. It is capable of producing muzzle velocities of up to 1,500 feet per second, which can generate a significant amount of stopping power. However, the 44 Magnum is not a rifle cartridge and is generally not considered to be an ideal choice for stopping a grizzly bear.
In general, it is recommended that hunters and hikers carry a rifle chambered in a more powerful cartridge, such as the 454 Casull, 460 Magnum, or 500 Magnum, for protection against grizzly bears. These cartridges are designed to deliver more energy and penetration than the 44 Magnum, which can help to stop a charging bear more effectively.
That being said, a well-placed shot from a 44 Magnum can still be effective against a grizzly bear, especially if the shooter is skilled and able to hit the bear’s vital organs or central nervous system. It is important to use high-quality ammunition that is designed for hunting or self-defense, such as hard-cast lead or copper bullets that are capable of penetrating through the thick hide and bones of a grizzly bear.
In general, it is also important to take other precautions to avoid a confrontation with a grizzly bear in the first place. This includes making noise to avoid surprising the bear, carrying bear spray as a first line of defense, and being aware of your surroundings and the behavior of the bears in the area.
In conclusion, while a 44 Magnum handgun can be effective against a grizzly bear in certain circumstances, it is generally not the best choice for stopping these large and dangerous animals. It is important to carry a rifle chambered in a more powerful cartridge for protection against grizzly bears, and to take other precautions to avoid a confrontation with these animals in the first place.