This Lee Precision Large Series 3-Die Set is perfect for reloading black powder ammunition for your 577-450 Martini-Henry rifle. The set includes three dies that are specifically designed for this caliber and thread size (1-1/4x12). Made in the United States, this high-quality reloading equipment is a must-have for any serious hunter or sportsman. With its precise and durable construction, this reloading set is built to last and to deliver accurate and consistent results every time. So whether you're a seasoned shooter or a beginner, this Lee Precision 3-Die Set will help you achieve the performance you need to succeed in the field.