The Well-Groomed Reloader: Cass Trimming

No matter how fancy your case trimmer may be, trimming cases properly can make reloading easier. If you don’t trim the cases, things could go wrong. Brass will stretch over time, even after multiple firings and resizing. The brass tends to flow from the bottom of the case towards the mouth, which can cause the case to become longer. It is important to trim the pistol cases. The case mouth is used for headspacing in most cases of auto-loading cartridges. Although it is not common, it is possible for the cases of the.45 ACP and.40 S&W to stretch to the point that the chamber is too long. If I have used my pistol cases for several firings, I will often check the length to determine if they need trimming. Revolver cases, however, will need to be cut to a uniform length as they use a roll-crimp to hold the bullet in place. The roll crimp is typically applied through a small shelf on the inside of the seating device. The die will be in a stationary position so you can see how a short case will give a very slight crimp, while a long case will create an excessive crimp, causing the case to roll too hard. Once you have your cases cut to a uniform length, you can adjust the roll crimp to ensure that the projectiles are held in the right amount of force. Bullets must be crimped in order to prevent them either from pulling out of the case mouth due to recoil in the magazines or being pushed further into it. This is especially important for cartridges intended for lever-action rifles that have tubular magazines. The bullet of one cartridge is pushed against a base of the other cartridge and if the bullet isn’t properly crimped it will move further into the case even after being loaded multiple times. Uniform case length equals a uniform roll crimp and that can make a big difference in pressures and velocity.Trimming ToolsLooking at the tools available for trimming cases, you’ll see a diverse selection, from the simplest hand tools to motor-driven, micrometer-adjustable machines. Among the simplest–and yet wonderfully effective–is the Lee Case Length Gauge and Trimmer (street price less than $25), which uses a cartridge-specific shell holder and a length/caliber-specific gauge, combined with a cutter to trim your case to proper SAAMI-approved case length. Although it requires some elbow grease, the unit can be easily adapted to an electrical drill to make your life easier. The length gauge is piloted through a flash hole in the case to get a square cut. There’s also an electric drill adapter that can be used to make smaller cuts. The case’s base is held by a collet and the mouth against a cutter. The user can adjust the length of the case by turning the handle. Redding 2400 Trimmer. Massaro Media Group. The motor-driven trimming tools can trim a lot without causing damage to your wrists or fingers. I own a micrometer adjustable RCBS Universal Case Prep station (street price $550), with a variable speed motor. It has been a reliable tool over the years. It is very useful when I need to convert brass from one cartridge into another. The micrometer allows you to quickly dial in how much to trim. The pilot is caliber-specific and keeps the cutter face as straight as possible. The motor is cut off when you depress the handle. Consider how much reloading you are planning to do. If it involves only a few calibers, a simpler setup might be a better investment. A Note on Length: There is often a debate over how long to trim your cartridges. The SAAMI-specified length may be listed as one dimension and then a trim to dimension, which will be slightly shorter. Because I use new cases often and don’t like trimming new brass too much, I tend to stick with the longer SAAMI dimension. It can reduce the neck length of some cases (e.g..300 Winchester Magnum). You can trim the neck a little shorter to keep everything uniform, new and old, but it is possible. Target grids and bullseye sizes can be downloaded in MOA. This is a great option for long-range shooting. Enter your email address below.