1. Dies. Use full length regular or full length small base dies. Small base full length dies size the case down a little narrower than regular full length dies. This is to improve chambering and lockup reliability in auto-loading rifles. However it is very possible you will have flawless chambering and lockup reliability in your auto-loading rifle using regular full length dies. If you have an auto-loader with a particularly tight chamber, desire extended reliability with a dirty gun, if regular full length resized cases don’t function reliably in your firearm, or if you just want to use small base dies, use small base dies. If you want to work the brass less and potentially get a few more reloads out of your cases, then use regular full length dies.
Keep track of the number of times you have fired a case. Always inspect rifle cases for signs of failure or imminent failure, particularly in the case-head region. Discard old rifle cases before you get case-head separation.
Be aware that auto-loaders do not fire-form cases to the chamber. The action of an auto-loader is fast enough that the case is still expanding and distorting as it is extracted from the chamber, particularly at the rear of the case. You cannot rely on the fire-forming cases when using an auto-loader.
Do not use neck only resize dies for auto-loading rifles. Neck only resizing dies are intended for bolt action rifles. Chambering and lockup is less of an issue with bolt action rifles for two reasons. First is that you are manually camming the bolt shut and can impart much more chambering force than an auto-loader action can. Second, since the case remains in the chamber throughout the entire firing sequence, fired cases from your bolt action rifle are fire-formed to your chamber, so they should fit to begin with. Neck only resizing is used in conjunction with bolt guns to ensure proper neck tension on a reloaded bullet in a reloaded cartridge.
2. Lube. Using good case lube and applying correctly is important for resizing rifle brass. If you are used to not using lube with carbide pistol dies, don’t try to carry this procedure over to rifle brass. After trying a variety of lubes, the very best by far is Imperial Sizing Wax. Imperial #07600 can be found in 2 oz cans for less than $10, and one 2 oz can will last a few thousand reloads. Simply apply the wax with your fingers to the body of the case as you pick them up to resize them. Regardless of the type of lube you use, do not get lube on the case shoulder. This can cause the shoulders to dent. If you notice shoulders beginning to dent but you are not putting lube on the shoulder, it is time to clean the lube out of your resizing die. I use a standard cleaning patch and rod.
3. Military brass. Once fired military brass takes some special care the first time you resize it, presenting two unique issues. First, fired military brass is usually oversized because it has usually been fired from full-auto firearms which have larger chambers for reliability and fast actions. This makes the resizing effort a bit harder, be prepared to really crank on the lever. Second, the primers pockets are crimped, making them harder to push out. I’ve noticed that when you really have to crank on the lever to resize a case, the likelihood of bending the decapping mandrel and breaking the decapping pin is higher. So, the first time I reload military brass I resize them first without the decapping mandrel in place, and then put the mandrel back in and run them through again to decap them. This will ensure you don’t break decapping pins or bend your decapping mandrel. After the first reload, this extra step is no longer necessary. For non-military brass, or brass fired from your rifle, this extra step is usually not necessary.
4. Primer pockets. For military brass you will need to remove the primer crimp so you can push new primers in. I use the RCBS Military Crimp Remover. The large is RCBS #90387 and the small is RCBS #90386. Use the large for large primer pockets and the small for small primer pockets. I simply attach an 8-32 coupling bolt to the screw on the back of the tool and chuck this into a hand drill to use it. These tools cost about $20. If you want you can buy a case prep center that this tool will screw into, but I find the expense unnecessary. You can also use the tool manually with a tool handle.
You may want to clean your primer pockets with a pocket cleaning brush as well. I usually skip this step, instead just checking that the flash holes are clear. I have never been unable to seat a primer properly. I have also not noticed any effect on accuracy. If the pockets are dirty enough that primers become hard to seat then I clean them.
5. Use a Case Gauge. A case gauge such as the ones produced by Lyman or EO Wilson. For example the Lyman #7832323 for .223 Remington and the Lyman #7832321 for .308 Winchester. These gauges cost about $20. If the case can drop into the gauge then it is resized to safe dimensions. Also, if the cases need to be trimmed the necks will stick out of the Lyman gauge. I find this to be the fastest and easiest way to check if I need to trim my cases.
6. Case Trimming. Case necks lengthen after firing-resizing cycles. When a cartridge is fired the case expands and the brass at the case head thins. When you resize the case, the diameter is reduced back into spec, but the brass doesn’t thicken, it lengthens. This is why rifle brass eventually wears out and fails, and also why cases need to be trimmed. I only trim cases once they protrude from my Lyman case gauge, at which point I trim them to the minimum spec’d length. This is so I don’t have to trim them as often.
To trim cases I use a basic manual Lyman case trimmer. Every reloading manufacturer makes one. I chuck the end of the trimming mandrel into a hand drill to make it easier and make trimming go faster. Lyman makes a replacement mandrel with an adapter for a hand drill already on it, or you can make your own.
Debur your case mouths inside and outside with a deburring tool after you trim them. I use a basic hand-held tool for this. There are many options available for under $20 and they’ll all serve the purpose.
7. Loading. It is now time to load your processed rifle cases. Prime them, weigh your powder, and seat your bullets. I like light loads for target shooting, but for auto-loading rifles do not try to reduce the load below the minimum recommendation. This will affect reliability of function of the auto-loading rifle. What works best for me is somewhere between the minimum and the middle of the recommended range. Use an official reloading manual.
Set up your die to seat the bullet such that you are at the recommended cartridge OAL. Measure OAL with a standard caliper. It may be useful to have a bullet puller available while setting this for the first time Use little to no crimp on rifle bullets without a cannelure. Even if your bullets have a cannelure, use only a light crimp.