Redding Trim Die for 45-90 Winchester. Redding Trim dies allow you to file trim your cases without unnecessary resizing because they are made to chamber dimensions. For case forming and necking brass down from another caliber, Redding Trim dies can be the perfect intermediate step before full length resizing. To trim your case using a Redding Trim Die, simply run a case into the Trim Die and if it sticks out above the die's top then the case is too long. File the case down until it is flush with the top of the die, then deburr the case mouth using a deburring tool. This die is quite useful when a considerable amount of material needs to be trimmed off in reforming operations.