For those of you who have never before processed .223 brass / 5.56 brass, we thought it might be helpful to provide a quick "how to" guide that walks you through the necessary steps. There are a lot of informative videos available online that we would recommend as well, but it can be nice to have a written checklist as a reference point.
Step 1: Cleaning
If you're starting with "raw" or "dirty" range brass, it's important that you clean the cases prior to running them through any of your reloading dies. Indoor range brass usually only requires a wet-tumble without any added media, but if the brass has been outside in the elements and is showing signs of tarnish, corrosion, or heavy debris build-up, we recommend adding stainless steel pins to your cleaner to help provide a source of abrasion. Doing so will not damage the brass, but it will give it a deep clean both inside and out. Cleaning brass is the most labor-intensive and time-consuming step in the process (especially when you account for drying time), so if you prefer to skip it you can always purchase pre-cleaned .223 brass / 5.56 brass. If you do choose to clean your own brass, we recommend using a mixture of dish detergent and citric acid.
Step 2: Inspection
Once the brass has been cleaned and dried, it's important to hand inspect the cases to check for signs of damage that could lead to failure. This could include cracks in the neck, crushed case mouths, or major dents or scratches. For more detailed information on inspecting cases, we'd recommend reading our article on Rifle Brass Lifespan.
Step 3: De-Priming / Re-Sizing
The next step is rather straightforward. All cases must be lubricated and then run through a combination de-priming or "de-capping" die that also acts a re-sizer. This will remove the spent primer while also addressing any expansion that would have occurred when the round was initially fired. The die will return the brass to its original SAAMI specifications (with the exception of the overall length) and expand the neck so that it is able to receive a projectile.
Step 4: Swaging or Reaming
Step four typically only applies to military 5.56 brass (i.e., cases with a Lake City headstamp), because these are manufactured with a crimp around the primer pocket. NATO military ammo is produced this way to ensure that primers do not become loose and fall out. New 5.56 x 45mm NATO ammo packs a "hotter" charge (hence the slightly thicker cases walls relative to .223 Remington brass of the commercial variety) and the crimped pockets prevent the heavy pressure from pushing the primers out of the case. Before military brass can be reloaded, these crimps need to be removed with either a primer pocket reamer or primer pocket swager tool. With reaming, the crimp is actually cut away. Swaging, on the other hand, smashes (for lack of a better word) the crimp so that the casing is capable of easily receiving a new primer.
Step 5: Trimming
Because brass stretches and lengthens when it is fired, the cases need to be trimmed to bring them back to the proper length. For .223 Remington brass, this is 1.750" +/- .003" (as a side note, the proper length for .308/7.62x51mm brass is 2.005" ± .003" and for 300 AAC Blackout brass it's 1.358"). There are a number of commercially available trimmers available for this task. Use a set of digital calipers to make sure you are within the proper range of length. Once the brass is trimmed, use a chamfering/deburring tool to remove any rough edges from the case mouth.
Step 6: Final Check
At this point, your brass should be fully-processed. We recommend employing the use of a 223 case gauge and a primer pocket gauge to spot check your brass for proper dimensions.
Step 7: Finishing Polish (optional)
While certainly not required, some may choose to tumble polish their cases at this point using corn cob media to remove excess case lube and any remaining brass shavings.