Which commercial gunpowders are progressive powders and why?

Progressive powders, also known as temperature-stable or magnum powders, are designed to maintain a consistent burn rate over a wide temperature range. This makes them particularly suitable for use in magnum cartridges and semi-automatic firearms, where high pressures and temperatures are encountered. Some common progressive powders include:

- Hodgdon H110: H110 is a versatile powder that can be used in a variety of calibers, including .357 Magnum, .44 Magnum, and 10mm Auto. It is known for its high energy output and ability to produce consistent velocities.

- Accurate No. 9: Accurate No. 9 is a popular powder for magnum rifle cartridges, such as the .300 Winchester Magnum and the .338 Lapua Magnum. It offers excellent accuracy and consistency, making it a favorite among long-range shooters.

- Alliant Power Pro 300-MP: Power Pro 300-MP is a high-performance powder designed for use in magnum pistol cartridges, such as the .357 Magnum and .44 Magnum. It provides high velocities and reliable performance, even in extreme conditions.

- IMR 4227: IMR 4227 is a versatile powder that can be used in a variety of rifle cartridges, including the .223 Remington, .308 Winchester, and .30-06 Springfield. It is known for its accuracy and consistency, making it a good choice for both target shooting and hunting.

- Norma MRP: Norma MRP (Magnum Rifle Powder) is a temperature-stable powder designed for use in magnum rifle cartridges, such as the .300 Winchester Magnum and the .338 Lapua Magnum. It provides excellent accuracy and consistency, even in extreme temperature conditions.

These progressive powders are designed to provide consistent performance over a wide range of temperatures, pressures, and barrel lengths. This makes them ideal for use in magnum cartridges and semi-automatic firearms, where extreme conditions may be encountered.